With rides like PBP and LEL the biggest problem would be no access to the controls. Whilst it's perfectly possible to source food and sleeping arrangements elsewhere, it'd be a huge pain in the arse.
Also, the motivation for "just doing it" is going to be less when you're not being tracked and your name won't be on a list of people who completed it.
As an example: running the London Marathon route without entering, or on a completely different day, doesn't get you on the list of official finishers. You can still post it on Strava though and you've still run a marathon.
With rides like PBP and LEL the biggest problem would be no access to the controls. Whilst it's perfectly possible to source food and sleeping arrangements elsewhere, it'd be a huge pain in the arse.
Also, the motivation for "just doing it" is going to be less when you're not being tracked and your name won't be on a list of people who completed it.
As an example: running the London Marathon route without entering, or on a completely different day, doesn't get you on the list of official finishers. You can still post it on Strava though and you've still run a marathon.