Reuse them for as long as you wish. Long as YOU are the only one using them, no issues at all.
Most of us with any experience remember VERY well, when you could cut up strips and make ONE strip last 3-5 tests purely because the results were colored and you visually atched them up to the closest color on the bottle(s).
Golly gee they went off the market quick… wonder why that is….??? (ssi)
Same with syringes btw WITH a few more restrictions, if you use them more than once. Easily done provided you only use one syringe designated for whatever insulin you take. Can't use the lantus syringe in the homolog, human vial(s)/pens…
Gotta stay designated to one insulin only. IF so use them until the lubricant on the needle fails, the markings start to fade. Either case its time to use a new one… IMHO-fwiw