Side effects of T replacement

I’ve been on testosterone replacement therapy for two months. I’ve opted for Androgel instead of Androderm (patch) or injections. I’ve tried using a little “extra” once before a workout and was quite supprised at my increase in endurance and recovery. From reading other forum posts there are several here who have experience with T supplementation.

By the end of a day should one feel a bit tired? (Pre-therapy levels of fatigue were significantly more intense).

No, all else being equal, extra androgen does not make one feel tired at the end of the day.
The opposite in fact.