^^ You should not have a problem keeping 10 out of 20 lbs as long as you continue to lift, eat properly. I personally tend to gain fat during PCT, so my diet gets priddy strict as far as the type of cals and amount of carbs.
As far as jumping back on in 8 weeks after a 13 week cycle. It just depends on your goals. I rather not have to be on TRT so I go {Time on cycle +Time on PCT= Time Off }. The longer I wait between cycles, the better I feel when I jump back on.
But I must admit, I have been running several mini cycles 4-6 weeks on short esters and love it. After my summer blast, I will be taking 3-4 months off.... maybe. :0