Oil issue

[Fazerider]

Warming it up once a week probably added a lot of condensation to the oil.
The level may have a bit low to start with, though not enough to cause the light to come on with the bike static.
Go for a prolonged ride and the sump finally gets warm enough to evaporate some of the water out and the level and density of the mayonnaise drops and the light starts to come on during acceleration.
An oil change and letting the bike get properly up to temperature every time should solve the problem.