I play another game some of you might know,Wurm online.It offeres a mechanic which gives the players double experience for a certain period of time if used.It can be activated and deactivated at any time.I recently started playing again and I think it's something that would really help with grind in istaria . Maybe not the best of suggestions but i thought it would be worth a mention.

In wurm online it's called Sleep Bonus,to regain sleep bonus you sleep in a bed or use sleep powder...