Some protocols said the ethanol will dry tissue out.  If you continued to next step, add cell lysis buffer you can leave it for several days at room temperature or add cell lysis buffer and proteinase K and leave it at 550C for several days (make sure your water bath is not dried up).  Hope this helps.

Thanks a lot! I I left the samples in lysis buffer at room temparature for 2 days. It seems that it worked fine.