Been my experience, as well. Could be a week, could be a month.
This one with a 100nm slit (BLK-CXR-SR):
Pretty broadband with good resolution.
I had purchased the spectrometer second hand. Bought a $$ custom fiber cable, a cosine correction optic, and a calibration source. While you can save a lot getting the spectrometer second hand, it starts to add up when adding the needed accessories. Not a handheld device. Instead a benchtop "lab" type device.
Ebay is a good source for such secondhand industrial / scientific gear. Sometime you'll find a gem. But, you have to be very careful knowing with what you are looking at and what you are getting. Like buying a classic car...
Not sure how good the calibration would be for anything below 380nm or so since the calibration light source I have isn't really that good for that range. But, the peaks will certainly be there.
This thread has some more info from some past measurements:
I've look at those as well. Very nice. In the end, went with the laboratory spectrometer to gain the flexibility and range. Disadvantage in my case, not handheld and a bunch of data manipulation.