Most productive sessions run 45 to 75 minutes including the warm-up. That is enough time for a thorough ramp-up, three to five exercises with proper rest, and a short finisher. Beyond about 90 minutes the quality of each set usually falls faster than the extra volume adds value.
Training results come from hard, well-executed sets, not from time spent in the building. As a session drags on, concentration drops, technique drifts, and the loads you can handle fall. You end up accumulating fatigue that costs you the next session while adding little to this one.
The other cost is adherence. A 90-minute session is easy to skip on a busy week; a 45-minute session is not. Over a year, the shorter plan you actually complete produces more.
Cut accessories, not the main lift. Keep the warm-up efficient, do your primary compound movement with proper rest, then pair two accessories as a superset of opposing patterns, such as a press and a row. Three focused sets of a squat pattern beat a rushed circuit of eight exercises.
Sessions genuinely run longer when heavy strength work needs three to five minutes of rest between sets, when you are training a skill such as Olympic lifting or a combat sport alongside strength, or when you deliberately combine two qualities in one block. In those cases the extra length comes from rest, not from extra work.
Look at your last set of the session. If it is noticeably worse than your first set of the same exercise, and that pattern repeats week after week, your session is too long or too dense. Trim an exercise and see whether the remaining work improves.