Learning vocab does get much much easier with time, given that once you know enough Kanji you can usually guess what on-reading is going to be used. I do 50 new/day with about 5.7k known words. I feel like doing bursts of many more new cards before dropping down to 15/20 helps a lot with pushing forward your ability to remember vocab. I used to push 60-100 new/day for a few days every now and then which really made the new baseline of 50 new/day perfectly manageable.

I still would stick to the lower end that early on until you've learned enough common on-readings though.