I don't know if I'm just built different, but I actually felt like the timer worked well in this game. It got genuinely tough in the final day, trying to manage all the potions with all the customers coming in so quickly. I think I probably only managed to get it perfectly since I'd stocked up on spares of every potion in my downtime on previous days. But I think part of the reason I did well was that I didn't spend much time admiring the TFs and reading potion descriptions. I think the current timer works well for this if it was a non-lewd game, but seeing as there is lewds to admire, I think the timed gamemode could do with a tweak of some sort. The easiest thing to do would just be to rename the timed gamemode to "time trial" or something along those lines, so that people who actually want to take their time appreciating all the TFs wouldn't try it. Possibly going along with adding a new "normal" mode, with more lenient timers. You could also add some sort of sandboxy between-day segment where you can read up on the potions and see their transformations on you, but I imagine that would be more difficult to implement.
All in all, I really liked the game. The art was charming and the TFs were very varied and fun to see. And the gameplay of trying to memorize potions and their recipes on the fly was fun! I feel like the gameplay might get stale if this was to be made into a full game unless you added some more mechanics to spice things up, but I think it stands well on its own as-is.