Neural improvements can appear within two to four weeks, which is why early progress feels fast. Meaningful structural change takes months, and serious strength takes years of consistent training. Judge progress in blocks of 8 to 12 weeks rather than day to day.
Rapid early gains come from better motor unit recruitment, higher firing rates, improved coordination, and reduced protective inhibition rather than new tissue, as explained in The Nervous System and Athletic Performance. Many people mistake this for a permanent rate of progress and become discouraged when it inevitably slows. Nothing has gone wrong; the easy adaptations have simply been used up.
Training age is the biggest factor, followed by sleep, calorie intake, protein, consistency, and how well the programme actually progresses. Age, sex, and genetics influence the ceiling and the rate but rarely change the direction. Someone training three times a week and sleeping seven hours will out-progress someone training six times on five hours of sleep.
Compare 12-week blocks, not sessions. Record the weight and reps for your main lifts and compare estimated maxes at the start and end of a block. Day-to-day performance swings with sleep, stress, food, and time of day, so a single bad session tells you almost nothing.
Check that the programme actually progresses, that you are eating enough, that you are sleeping, and that your technique holds at working weights. Those four explain the large majority of stalls. Adding more training volume is usually the last thing to try, not the first.