IMO the LE timer starts when they were asked to do a wellness check, and they responded quite quickly after that. Search warrants the day after learning Lori lied about the children's whereabouts? That's pretty darn fast.
I don't think LE can be blamed for the Sept to Nov gap. There are lots of legitimate reasons why someone's kids may be pulled out of school. Home schooling, illness, special needs private school, job transfer, living w/relatives or friends, etc. I imagine Lori can be charismatic and convincing when she wants and she's no dummy. I suspect she gave his school an explanation that was quite credible and there was no reason for them to contact LE.
As a rule I support LE but if I think they've dropped the ball I'll say so. IMO they've shown more urgency than several other cases we've seen recently and I give them the benefit of the doubt when they say no one would be working the case for two days. I have a hunch investigators were working the case through Christmas but the Public Info Officer and others who field press calls were rightfully given time off to spend w/their own families.