Increasing the time you hold a stretch is good, because you're able to relax fully into the stretch (deep into your inner penis) and maximize the temporary elongation after a session.
At the last 5 minute, you're able to stretch harder, then compare to the first minute of the 5 minute stretch.
You will be able to get away with less time and still gain effectively. Longer holds will be more effective for gaining faster.
So I would go with that, instead of getting in more sets. If you have more effective sessions/sets you do not need as much time under tension. But you need high intensity with this approach.
But if you can get in 1 session in the morning and 1 session at night that would be better, because due to the elongation healing.
That is: Keeping your tissue elongated during the hours between those sessions.
Here ara good videos about that:
03. Resting Time Between Penis Enlargement Exercises (FAQ video).
27. Healing Penis while Elongated (FAQ video).
There was one more video about plitting up sets during the day, but I can't find that specific video now. But it's in the same thread as the videos above.
Kind regards
SIM