Humidity Meters calibration using 'Salt Bottles'

[videobruce]

Specifically these items that I'm looking to purchase. I have a few questions about those and any other models, this is not my 1st rodeo with these;
https://www.tequipment.net/Triplett/RHT32/Psychrometer/
https://www.tequipment.net/Extech/RH300-CAL/Lab-Accessories/

I have had issues with a Martel C315 Humidity Meter (I believe the company is out of business now) which is the same as the current Amprobe TH-3 that is over 10 years old now.;
https://www.testequipmentdepot.com/amprobe-th-3-relative-humidity-temperature-meter-dual-display-extended-probe-and-capacitive-sensor.html

I haven't used it much lately due to the following;
What happens the unit looses it's calibration using their 'salt bottles' in a matter of months. So anytime I need to use it, it has to be re-calibrated.

1. How long are these models (not just this one I'm looking at) hold calibration?
2. How long are those 'salt bottles' good for (assuming they are kept closed and in a temperature proper environment. Same goes for the tool itself)?
3. How does one know these calibration bottles are still good?
4. Does one have to add more filtered water to those bottles after a period of time?

I have read, two years was mentioned for the lifespan of those 'Salt Bottles' which seems kinda short (of course depending just how often you calibrated the meter.