Most of my buying has been at train shows and I will impulse buy after some quick deliberation as to if I need it or really want it. I do that at estate and garage sales for just about anything, as I go to many more of them. I have learned to act quickly after seeing an item, being unsure and passing only to reconsider and go back to that table and it is gone. Once or twice I just put it back on the table and someone quickly picked it up and bought it.
I seldom buy on line and only have impulse bought a few times. On line has lost a lot of my interest with too many buyers bidding things up now and higher shipping and sales tax.
On line impulse buying worked out once when I bought alike new 0-8-0 switcher that was way more than I should have paid. It was damaged during shipping and the seller offered to let me have it for the shipping cost. I was able to fix most of the damage that was details I could glue back on and it runs great, which is more important than any minor damage or repairs to me.
Charlie