Oh, I wasn't saying don't do it, but check out the PIC Data sheet to see power consumption for weak pullups.
In a recent thing I did with a 16F886 I had to revert to external 1M5 pullups to get my power down. They may be called weak, but a current consumption of 250uA (ish) is quite steep for a low power circuit that could easily work at a tenth of that (average).