By the time the peptide gets to you, the 99% could be 94% and the 97% could still be 97%, so don't concern yourself too much with that. 96% or above imo is fine.
Pharma reconstituted GLPs (pens) last for two years under refrigeration. That's under perfect conditions you cannot replicate.
User reconstituted pharma proteins in multi dose containers, using the specific BAC they supply, are universally instructed to be discarded after 28 days.
No one can say for certain how long before a UGL peptide degrades. On top of all the variables, each batch will vary in stability as well.
What you can do to maximize its life is the following.
-Use real pharma grade BAC like Hospira.
-Use high quality syringes, like BD, to minimize the amount of silicone lubricant introduced into the vial when reconstituting. Silicone droplets promote degradation.
-Dilute to the same ratio used by pharma, or more, but never less.
-Exercise discipline in wiping vial top every time with an alcohol swab, and allow to dry, so you minimize introducing more bacteria.
-Of course refrigerate, protect the vial from light in an opaque container.
-Allow the reconstituted solution, in its opaque container, to come to room temp, 10 minutes or so before opening the outer container and using. This will prevent bacteria laden condensation from forming on the vial.
-Minimize vial agitation after reconstitution. Don't keep it in a refrigerator drawer that's frequently opened, for instance.
The more of these steps you follow, the longer Reta, or any reconstituted peptide will last.
Doing what you can / are willing to is better than not doing any of them.
All of that said, 7-8 weeks is rarely a problem, but it's always a good idea to protect as much potency as you can anyway. The products of protein degradation can have other undesirable effects.
For the truly obsessed:
-If you're really intent on doing everything possible to minimize any potential source of degradation, use a .2 or .22 PES low protein adhesion syringe filter and transfer the reconstituted solution into a sterile, pyrogen free container, at the cost of some product.
-Finally, the ultimate you can do to ensure you're injecting the best version of the peptide is to syringe filter the dose into the syringe just before administration.