My Lithops gracilidelineata (just like the dorotheae) were among the first Lithops I ever sowed and they are 4 years old now.
A while ago I wrote that I'll have to measure them... I am going to do that. Or at least try to remember to put a coin in my pics for comparison or something.
I am still waiting for any of my self grown Lithops to grow two heads during one winter. So far none of them have. That will be a very cool moment!
These gracilidelineata are my three biggest (and I think the only ones I kept) and they are doing so well. They "live" on the south facing windowsill in the corridor outside of our apartment and have to endure quite cold winters there. Apparently they like it.