When to upgrade

I am new to pumping, but not to PE. I’ve been using it as a warm up and a finisher in my jelq workouts. It usually goes like this

Pump - 5min.
Jelq - 5min.
Pump - 5min.
Jelq - 5min.
Pump - 5min.
Jelq - 5min.

Anyway, I’ve been doing this for about a month with a 10 x 2 gravel tube, and I went from packing the tube about 3 inches up after 30min. in the beginning to packing it 8-8.5 inches up after 20min. Am I due for an upgrade???? Is there a general rule for when it is time for a bigger tube??
I am guessing I should stick with this tube for another month or so to solidify gains, but I could use some advice. Thanx,

Stalyn