A friend of mine did something similar at a festival.
One of the major whisky brands was giving away free double measures in a small plastic glass. My friend kept going up every two hours until they recognised him and said .....here,s one of the regulars
In the end the vendor went and got a much larger glass, filled it to the brim and said ....there you are will that do ya .....lol
Loyal could I suggest you take a piece of sandpaper in your pocket and if they give you any grief just wave it in their faces and say...no blubbering lads.....