what's my levain trying to say to me?

Wonder if anybody can help.  Lately, when I make my final levain for a bake, it's still peaking after 24 hours  It just won't go done.  I don't think this is a bad thing, just a little unusual.  In the recent past, it would peak and then collapse like a good little levain.  Although not a bad thing in itself, what's my levain trying to say to me?  Is it the flour?  Lately the falling numbers have been in the mid to high 400; can it be that the yeast/bacteria acessess the food at a slower rate and can sustain a longer feed?  I don't know.  Cheers.