We use a system of "If it is an expensive or rare component you need to prove that you can provide it, but if it is common and/or cheap, it's assumed you keep a supply in your component pouch"
Our rules for what is rare/expensive are pretty arbitrary, but nobody has ever had a problem with them. A 100gp pearl for the identify spell is probably the best example of a common component that you need to prove you bought on a regular basis.
I think our reasons for this are a holdover from 2e, where mages had a tendency to suck REALLY bad at low levels, and it made people even less interested in playing them if you limited their spells even more with component regulations.
But I could see the fun in having strict rules about components.
My guess is that most people will not have strict rules about components, but I'll be interested to see if that is correct.