I usually reconstitute only right before I need it, though I've been eyeing something along the lines of what @indolent does. My KLOW protocol runs 75 days and uses two GYC vials, which comes to 24 ml total for me because I mix it dilute to avoid bruising. That leaves me with the final 6ml, and I've been thinking about putting it toward tirz instead. If I do that, at 22 mg/ml I'd end up with 132 mg of tirz, roughly four 30 mg vials, which at an 8 mg dose would carry me through 16 weeks. The plan would be to freeze whatever vials aren't in use, and that way a single bottle of bac water stays in play for under 30 days from opening. The timing I have in mind: recon the first KLOW vial and the tirz together at the start, then recon the second KLOW vial 38 days later to finish off the remainder, since KLOW might break down quicker.
(indolent reconstitutes a whole kit of tirz at once and freezes it, but that feels like too much commitment for me. What if I end up dropping tirz and switching to reta for years?)