I have those. Im looking for a new pen. My last one never failed me. I hate the strips. Cant stand them
Thatās a sad day hombre! 
I love my BlueLab pen.
Doesnāt one of the other high-end pens, like Hannah or Apera, offer a replaceable probe on theirs?
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Yea, just saw the apera one and it looks like what i may lean towards. I just cant do drops or strips. I have them as back up but i like to be exact so i can record exactly what im doing and dial in. Im a little OCD that way tbh.
Im a big fan of knowing what my EC/PPM and PH are at all times. Still using my blue lab truncheon for monitoring EC, going on 10 years with the same one. Beast.
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I also keep the strips as back up.
But I love my BlueLabs.
Oh, I know this all to well my friend.
I grow organically, but still check my water quite frequently! 
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Lol, nice. Yea im in pro mix HP, salt based nutes, RO water system and usually using autopots to auti feed 20-30 plants so i really like to be on top of things as things can get ugly if not kept in balance. I run organic outside and still PH too!
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We have a Bluelab PH pen that we use, going on ~6 years. Calibration has held well with minimal offset or drift. Knock on wood.
PH pens do have a lifespan and we consider them a consumable. You should be able to get at least several years out of a good probe. We didnāt expect the Bluelab to hold up as long as it has and I feel that weāve gotten our monies worth.
Biggest issue is remembering to ensure that the storage solution doesnāt dry out during the off-months. The probe will survive for awhile even if the storage solution dries but it will eventually start to dehydrate the bulb, concentrating the bulb solute, and, if allowed to remain in this state, may damage the probe beyond recovery. At that point, it may not be possible to produce accurate readings, the probe may not maintain calibration, or the reading will drift up or down while measuring a static solution. There are a variety of potential failure modes but Iād surmise that drying of the probe is the most common.
We purchased a liter of solution from a good vendor and use that across a variety of probes. Doesnāt take a lot and we have still have several of years of solution left.
You can make your own storage solution inexpensively or purchase the storage solution. Key for longevity is to keep the bulb moist with the storage solution. Key to maintaining calibration accuracy is to keep the bulb clean and to use the same storage solution formulation that was used at the time of calibration.
Calibration has maybe been once a year at best, for us. Between calibration cycles, the drift and offset has shown to been minimal so far. Or, I should say, the variance is less than could be reliably quantified with the PH paper approach.
Cost is many multiples the cost of PH paper, of course. Though the convenience and precision is worth it to us.
Probes are part of our maintenance schedule, likewise oil changes on our engines. Both require the occasional love to head off the problems.
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@Northern_Loki Very well-written summary there!
Iām liking my Apera PH60. I also purchased a larger bottle of storage solution than provided with the meter. The Apera design is nice with a seal on the cap to keep the probe wet when stored vertically.
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There are quite a few fans of the Apera probes. Probably in the same class as the Bluelab probes though maybe more cost effective? I have my eyes on those and may pick up one once our Bluelabs probe gives up the ghost. And, good to see a better seal. There really isnāt much to the sealing with the cap on the Bluelabs.
(I like the stand)
Oh, and keeping the probes vertical during storage is a good point.
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I think they are actually in a performance tier slightly above the Bluelab pH pen - 0.01pH resolution vs 0.1pH. The replaceable (and economically reasonable) probe and nice self-sealing cap design swung the balance towards Apera for me.
I want to come up with a better stand for 3D printing so folks can make it easily here. The ORP meter is stored in the same manner as the pH meter, storage solution in the lid but I added a similar seal ring like the Apera came with.
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My bluelab PH pen is still kicking but maybe on itās way out.
8 years old, it stopped calibrating this year, just gives an āerā when you try.
It reads 4 and 7 ph standard as 3.9 and 6.9 respectively.
I never used any storage solution and have let it dry out several times by leaving the lid off or not using it for 12 months+ which makes me wonder how long it would of lasted if cared for a bit better.
Their EC pen is also good, only 0.1 resolution but thatās honestly fine as thatās as precise as Iāll ever be working to.
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Thatās a very good lifespan.
The sensing element on probes will develop an offset over time and the slope across the range trends towards zero ā¦ meaning it becomes insensitive to differentiation of values at differing PH. Calibration cancels out those effects but eventually it will run out of runway, so to speak. Also, reading stability can be impacted as that progresses.
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Ended up going back to what i know and ordered another blulab. Thanks @Northern_Loki for the detailed info. The blulab never failed me. Cheers everyone
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