Too true, I couldn't agree more. I'm a one man band with my compound next to me, I stopped Sundays about 3 years ago, IF I've received a deposit from a customer who has already viewed & test driven (so it's just 5 minutes for the money & log book exchange) then I'll let them come before 11 o'clock.
Viewings, test drives & collections without a prior viewing are a no no. 99% of them tip up late without an apology, want to piss about like the messers they are, fancy driving a few (phone up about a £700 trade in & take a fancy to a £4000 Jeep) and then go away to think about it never to be seen again. They all seemed to be on their way to the shops, turned up late after a pub lunch or have simply exhausted themselves looking around B&Q every Sunday and fancied looking at cars instead of patio decking, lampshades & potted plants.
Strangely about 4-5 years ago I often did a few on a Sunday teatime but now any sales are generally Mon/Tue & Thur/Fri with a busy Saturday perhaps once a month, but usually my Saturdays are dead (except yesterday) with the odd messer fancying a spin in one of my cars amongst the other 6 they're going to see.
Dont be afraid to sack-off the Sunday brigade. If your cars are right & your prices are right the genuine punters will still be there on Monday.