Going back to the OP’s post, although I like to keep my eyes on the car market, so I know what is available at the time I am due to order, a few things I never do are:
1. Check the AP of a vehicle after I have collected it – I would rather not know if the Advance Payment has gone down after I have got the vehicle.
2. Look at ‘updated versions’ of the car I currently have – again I would rather not know that it now comes as standard with something that I ordered as a paid option.
3. Look at the quoted mpg – I get what mpg I get, not what is quoted.
Re 1 above, I do the same when booking flights, holidays etc. As long as I am happy with the price I paid (and I wouldn’t have paid it if I was unhappy with the price), I never ‘recheck’ the price because there is bu**er all to be done if it is suddenly cheaper at a later time. I would just rather not know.