Sorry about the stones! I've had stones chronic since I was 19 or 20. I'm now 46. about 4 yrs ago I had to have a stone blasted for the first time. I think only a qualified urologist can tell you for sure if it's too long to wait. the DR. usually puts in a stent while waiting to keep the stone from blocking the ureter tube so you can still urinate. the "sand" if blasted properly is usually so small you don't normally feel it. You will be under anethstesia for the procedure, so you won't feel a thing during it. you might be a little tender in the kidney area for a day or two but that's about it.
Just remember to drink lots of fluids after the procedure.