You can do them as long as you scale the weight appropriately and don’t allow form to breakdown, that would be around the 10 rep ranges. Going as high as 20, I’m not sure.
I’ve been doing for a while deadlifts with strength sets (5/3/1) followed by 5x10 snatch grip deadlifts and I’ve survived, so it can be done.
As JMaier stated above, you’ll surely have hypertrophy gains from them to some degree, but the eccentric phase is a big portion of hypertrophy gains and slow eccentrics with deadlifts for high reps doesn’t really sound like a good idea. I guess that romanian deads are a smarter choice as mass builders because they allow slow controlled eccentric on each rep, are less prone to form breakdown and overall seem more sustainable on the long term.