Welcome to the forum!
To your question:
It all depends on the conditions you grow the plant in.
If you have a lot of light, CO2 and fertilisers, you can have a much bigger plant (bigger than 30 cm high) in say, 1-2 months. If you have less of everthing, it can take many months.
P.S. E. bleherae (note the spelling) has been synonymised with E. grisebachii (as well as E. amazonicus and E. parviflorus).