[libvirt-users] what is the practical limit on snapshot generations?

I've googled around on this and haven't found much so I'll ask here. I have a client who routinely does live snapshots on snapshot on snapshot ( just keep going recursively) I've told him to roll them up once in a while, but he feels its unnecessary and only plans a rollup during a major maintenance period, where he can take the whole site down and then watch it grind during the commit. Note these are Qcow2 (1.1) images and they are external snaps. Most of the write activity is logging and medium database writes for an ecommerce store. It is certainly NOT heavy write i/o. Isn't there a cost (speed, resources) etc to all those generations. Any safety issues? Is there an optimium # of generations where if you exceed that you get diminishing returns. At one point are you shooting yourself in the foot, or is this really no big deal aside from two hours of downtime while the 'actual' commit occurs. -wk