I'd say one person over ~12 years is basically multiple developers working on it. I look back on code after a couple months and it often feels like someone else wrote it.
Yep, and in particular, one person over 12 years with one to three month breaks between sessions of working on it. He had no choice but to "monkey see, monkey do" what his past self did, and the resultant product is ... difficult to maintain, to put it nicely.
[Edit: I don't blame him - I understand how it happened, and also why he wanted to get out ;)]
