If you end your cycle and go straigt back to your trt dose it could be 3+ months to go back because every time you pin your 120mg your slowing down the hormones coming back to range. It takes 5 half lives to eliminate s drug so id stop pinning for at least 3 half lives of the drug to get levels significantly down Before going back to a trt dose.
400mg of test e, half life is around 10 days, you can find all kids of conflicting info on this but It's pretty widely accepted that it's about 8-10+ days.
3 half lives is a month
Finish your cycle, wait about 4 weeks and your testosterone should be back around trt range by then and you pick back up your trt protocal at this point.
If you wanna split hairs and get super accurate Then look up one of the steroid planner charts. You can enter the drug name, injection frequency and dosage and it will show you how long to peak and eliminate the drugs.
Dont rember the site off top of my head but theres a few.
Better option for someone whos worried about trt bloods and red flags would be safer using short esters and low toxicity orals (on Occasion)
Test (trt 120mg per week) keep it that way.
Add 75-100mg test prop eod or 3x week
After you finish the prop you skip a week of trt and then go back to normal. Again this is a estimate, you can use a steroid plotter to figure it out.
Some quick acting blast options...
*Test prop
*Mast prop
*Npp
*20-30mg of most orals will present minimal stress in short 6 week runs
*hgh yiu could stay on and that would help you get more out of lower gear doses
*insulin if you know what your doing