Lots of paranoia here:
- Odor...not significantly different than 2-3 days holding...as long as your vent is clear no reason to expect a build up of odors.
- Solids...1/2 to 3/4 full should be fine, the solids will actually break down naturally (that's how a septic tank works) and there is enough water that it's not going to dry out.
Where you could run into trouble is if it's only got an inch or two of water in the bottom and it evaporates over a few weeks leaving the solids cemented to the bottom but as long as it's not all the time, it shouldn't be a big deal.
