[Dovecot] frequent index rebuilds versus disabled indexes

Ok, here's the short and sweet version of my dilemma. I have a group of servers mounting a shared NFS device to hold mail data for many different domains. Is it worth the load balancing management nightmare of setting up dedicating smtp, pop, and imap to one server (failing over to another in the group if the server goes down) to keep indexes on local disk? It's very tempting to just disable indexes and not worry about which server a user hits, and considering the vast majority of our 170,000 accounts only have about a 20MB quota, I'm not sure indexes will help that many users. Although, I guess I would need to work out something for the few huge accounts we do have.