Have had high-priority issues show up half-way through two days in a row now, pulling me from one client to another. Result has been 11+ hours billable each day (on top of not being particularly rested from the weekend). I'm getting well toward mind-numbed.

Some (tired) thoughts:

Pre and post condition checks are good things in maintenance code-bases. Sanity checks for the "no way that can be that" stuff are a very good idea. Particularly good idea if you're going to work on a code-base for long enough that you won't remember the original plan when you're implementing new stuff. Simple asserts are fine, after all, there's no way that could ever happen ;) .

Reporting is key in accounting. It may seem that the ledger is the key, but no, the ledger is easy and straightforward, what's hard is making the visualization such that people can see any problems as soon as they show up. You don't want the situation to go unnoticed and have months of work based on it.

Sleep is good. Sleep.