|image from sixthseal.com|
The safe answer here is give to your heart's content. But my dear, practical friend from Singapore (you-know-who-you-are) would always put an economic perspective when it comes to paying "extra" for "extra" services.
He determines the "minimum wage" of the city as part of the equation. In Metro Manila, it's about a little less than 500 pesos.
So if you pay 500 to 1000 pesos for a few minutes of extra manual labor on you. Then you shouldn't feel bad about it. Majority of people in Metro Manila work harder for 8 hours for less than 500 pesos.
I hope this give you another perspective on the cost of the "extra" labor work that you request for.