I'm not sure what age you plan on retiring BUT
There are very few who can (or should) take up significant decompression diving at 65+yrs old. Most tech divers are dialing back their risks and exposures starting in their mid-60s and limiting themselves to "tech-lite" stuff, not just starting to build their experience in decompression.
The DM is the start of the path towards working with students. You could do that now or when you're 70+ yrs old.
If you are just taking AN/DP or Tech40 or Tech1 etc for fun that's fine too. They will all get your fin in the door at the tech-lite level and give you a bit more knowledge than the average recreational DM.
There are very few who can (or should) take up significant decompression diving at 65+yrs old. Most tech divers are dialing back their risks and exposures starting in their mid-60s and limiting themselves to "tech-lite" stuff, not just starting to build their experience in decompression.
The DM is the start of the path towards working with students. You could do that now or when you're 70+ yrs old.
If you are just taking AN/DP or Tech40 or Tech1 etc for fun that's fine too. They will all get your fin in the door at the tech-lite level and give you a bit more knowledge than the average recreational DM.