So, when I was growing up, my mother said to me, over and over..."You never finish anything you start!"
Same here. I'm also a perfectionist so I've reinstalled and/or restarted neighbourhoods from scratch at least 30 times since I bought the base game in September 2004. In fact, I did a reinstall for the NL patch just last week (Edit: I know it's not necessary but I do it anyway).

I think I started out creating me and my husband, got frustrated and moved on when I accidentally named our last child "Baby Boy" (before I figured out how to change names). Thereafter I mainly played and restarted Pleasantville, though I did enjoy a brief stint with Strangetown. I think I quit just as I had graduated all the player sims from La Fiesta Tech. Recently played a vampire for awhile but got bored because she didn't want children and you can only go clubbing so many times before it gets old. I kept wishing for a mod that would allow vampires to drain and kill their enemies.
Started again today with a new legacy family, deletedallcharacters and carefully selected/renamed new townies and NPCs. I'm trying to just go with the flow and enjoy myself because my last legacy family involved a script for the entire 10 generations, with the first 2 alone taking up five pages. Got boring and overwhelming because things would always deviate from the script and, well, we can't have that, can we? The last straw was when the vanishing memories bug showed up in the 2nd generation's uni-educated wife.
I think my play style sounds a lot like sagana's. I can easily clock in 8 hours a day, barring work, and mainly stick with one family the whole time (I really hate playing and aging other families to keep them in step with the main one). Then I get frustrated with, say, a lack of clothing options and go on a downloading spree for another 8 hours. I also tend to go on theme kicks--there was the Victorian England neighbourhood, the British-Asian neighbourhood, the ultra-hip gay neighbourhood, the hillbilly neighbourhood, etc. But I never stay with them long enough to fully enjoy the tons of work I intially put into them.
I also stay up really late during the first few days of play... Is it 2 am already?