Also using the older pen remnants @Usernameunavailabl There's less than half a dose in each so I'm just using it to taper up to 1mg so hopefully I don't feel as tired.
I'm on my second round of 4 x 0.5mg and finding it was wearing off a bit despite my initial optimism, so I took the first one as normal, the second one with the remaining bits from the 0.25 pen (kept out of the fridge and on my bedside table as I didn't know about the fridge thing when I got it first... and by this point 10 weeks old 😯), the next dose with the remaining bits from the first 0.5 pen (7 weeks old) and then with the last 0.5 dose from this pen I'll finish off the pen.
I did feel the increase when I moved it to 0.6ish and that's with me not minding it properly, so I would think if you've looked after it properly you'll likely see no loss of efficacy.
The scales says I've gained 2lbs this week though but I'm so bloated from my period I'm just waiting to see what happens when it's over.