2y/o= 12mos effective wear= 5 washes + a final dbl cold wash for final evo shots [*last 2 pix @bottom]
Thought this would be a good place to share.
These are my old Samurai 710xx 19oz, proxy'd them from Japan so I could have the tab and pocket details, back when Blue in Green was only selling pairs without any pocket details. I wore them for about 2+ years and they went through 2 crotch repairs and I think 2 washes. They still fit pretty good after trying them on today, a little more snug in the thighs as I lift more now. I may touch up the crotch repairs as they are fraying a bit and them put them back in rotation.
I think the fit looks great, they may stretch out a bit form where you are now in the waist and thighs but the rest should stay pretty much the same.
Are you planning on washing them regularly? If your are just going to wear them as long as possible without washing don't even worry about more shrinkage, just wear them and enjoy. If you are worried about shrinking when it does come time to wash, just have them dry cleaned but be sure to specify not to press them. Or hand wash them in cold water and hang dry. As long as they don't hit the dryer I doubt they will shrink much more.
I am the same when it comes to my denim too, I go typically at least a year before thinking about washing. Normally I would just hand wash them when the time comes. I did machine wash my 710xx a few times as I wanted to really see the fade contrast kick in. I probably waited almost 2 years before machine washing.
They will only stretch as much as needed, if they are not super tight right now the stretching will be pretty minimal. If they did end up stretching out too much you could periodically hot soak them to get them to shrink back up a bit. I have had success with a few pairs of jeans using that method.
Enjoy the new jeans and in a year or two of moderate wear they will look as great as my pair posted above. I just got the crotch reinforced on my 710xx and will be giving them some more wear on the weekends. The 710xx is a great cut, one of my favs.