My husband, in his 70s when diagnosed, was on AS for a year and it gave us breathing space.
No he didn't stress about it, he was quite laid back. m I found the approach of the PSA results a little nerve wracking but as Lyn says if it is done properly any changes can and will be picked up.
After that year of grace he did decide on treatment since the PSA went up.
It's easy to say "Whip it out and get it over with" but that isn't allowing for the after effects, which in some cases are not very nice.
Since he does appear to have the option of AS then at least for a while, it might be wise to first get your heads around having cancer then look at available treatments.
Don't accept that it is only AS or the op. If he has been given the AS choice then he dose have other options available to him, it's just that the consultant he saw only does surgery.
Ask to see an urologist and see what else is available