Although we don't currently dive we may want to one day so I went in & told them I wanted a mask that was rated to go down further than 30' and asked which ones they could fit with lenses & they pointed me toward a couple & I tried them on to be sure it fit & sealed properly. I think the mask itself was about $65 or so then the lenses were an addtional $50 or so. If your DH has a degenerative eye disease though there is really no way of knowing where his eyesight may be in 10 years. By the time he needs new lenses they may or may not be able to still fit the mask. That's something that you'd have to ask the shop where you go... The shop where I went last time didn't offer RX lenses for ALL masks, only some. Not sure exactly how it works.
You can add the scripted lenses your self if you choose, or have any shop do it, the only thing I storngly suggest, is that after you have that done, try the mask in a pool, bath tub or shallow lake, BEFORE you do anything else with it, to check for potential leaks.
For the most part, the same masks that you snorkel with, are the same masks that are dive masks. The Tusa Liberator snorkel set, for example, is the same mask I use to dive with, and have had that mask to 130' of water in the Keys.
Generally speaking, your face doesnt change much after you turn 18-20 or so. For the most part, though there are exceptions, the same mask will fit an adult for many years. The difference is that masks will detiorate,over time. The silicone will break down, seals will dry out, straps break etc. I still have my original mask with the script I had put into it, almost 20 years ago. My dad does also. Mine still fits me and my dad still uses his on occasion. I probably wouldnt trust it to dive the Spiegle Grove or the Oriskany, but I still carry it as a back up.( I wear contacts) Its all in how you care for it.
Alot depends on the size of the shop, for scripted lenses. I was talking to the owner of one of the lds near me, since they are the only ones that carry my brand of gear locally, and he was saying that a lot of the major manufacturers, are now saying that in order to carry a specific line, they have to invest in a large amount of money. Basically the shop would have to buy say 50 or 60,000 dollars worth of equipment, even if they only sell 10,000 a month.( I dont remember off hand how much they have to buy but it was in the high 5 digits.) Multiply that by several manufacturers and you now have a shop investing literally close to 500000 dollars,for inventory it may take them years to move. So they dont carry a lot of things that may not sell as much, such as the inserts for masks, or not the normal sizes like xxs or xxxxl.They carry what sells all of the time. Most shops I know of, at least here, if you ask for something that they dont have on the shelf, will generally order it for you. If they are a reputable shop, (There are some unscrupulus ones) they will point you to another shop, or online if they cant get what you need.
Now the bigger places, like Leisure Pro, Divers Direct, Scubatoys, who have multiple shops, and large inventories, have the cash to buy bulk, and get better deals, and carry more, then most mom and pop shop in a strip mall or stand alone.