TBH its something i only pull out of the cupboard in the cooler months (say from now till Sept). It doesnt get a look in during the summer months - but who wants casserole on a 40deg day. So for us, its seasonal.
I also tend to use mine more in the winter months too. I would most probably use it once every week-fortnight for things like stews, lamb shanks and currys. I also make a yummy corned beef in it, in fact I just bought a corned beef today with the very intention of pulling out the slow cooker over the weekend!

I dont have a problem with putting it on at around 10am and leaving it for the day whilst I come and go. I know of quite a few people who put it on before work and then leave the house for the day...I suppose it is just what you feel comfortable with really.