lysozyme solution storage - (Aug/17/2006 )

I wish to make a 20mg/ml lysozyme solution, aliquot and store at -20C, but I keep hearing that it is best to make it fresh every day. Why is that? Does anyone else freeze and then use? It will be used for DNA extraction from bacteria. I have been using freezing and thawing the same tube of lysozyme for two months ( a big no-no, I know) but it has been working each time without much problem.
Thank you.

I've never had a problem aliquoting and freezing away in single- or double-reaction volumes.

is this a diluted solution?
because mine once i dilute it i have to keep it in 4 degree for only one week if i put it into -20 it will loose its activity.