If you use T plus hCG than you will be fine, nothing to worry about.
But there are examples of persistent testicular failure and infertility due to long term T use out there.
The literature suggests that if you are low in T before starting TRT already, then use only high dose T for years thats what sets you up for problems.
The last article is an interesting one. It provides the probability of reaching a meaningful number of sperm following cessation of TRT and initiation of hCG therapy. The longer T was taken and the older the subjects were, the lower the probability was to reach 5 mil total mobile sperm.
But again the hCG when on TRT is a wonderful preventiv measure.