Next is there any special brand to get or to avoid if I do need to replace it, my current one is Counter Assault.
Edit: It appears I should have done more research, I found the following on Amazon
However I'm still more than interested in hearing other input.How long does it last when not used?
The expiration date is on every canister. When we buy direct from the manufacturer, the expiration is always at least 5 years away, and sometimes a bit more. However, even after it's peak effectiveness drops off, it will remain reasonably effective for a few more years, though I would suggest replacing it soon after the expiration date. One thing to keep in mind is that the expiration is set well before it actually looses effectiveness.
Keri-Lynn, Four Seasons Survival