I personally think 30-45 minutes is enough. But if possible without a 20 min solo soft warmup, which is usually boring. Make the warmup shorter (5 min) and more interesting than these fake sensual eye contacts... I'd like them to be more real.
Then for the scene itself, 30 min is enough to show some anal, DP and DAP. Last scene with Alexis is IMO too long for nothing. Putting 10 guys but letting them act one by one is useless...