When to move to mUlti-db


I recently was planning to move to multi-db, but now really dont want to bother when I learned there is no practical backup solution to multi-db. I would like to learn if I can make the transition to multi-db at a later time. I need not more than 100 subsites and it will be a long time before my network reaches much more than that. Is it okay to move to multi-db at a later time. For example when the network becomes 500 sites. Does it matter to do this transition when one has 5 sites or 500 sites.