Consuming hydrolyzed collagen should be thought of like any supplement taken to improve and/or support your health. If your body needs it, and you're not getting enough of it in your diet, you should consider continuing supplementation for as long as this remains true. A study published by the British Journal of Dermatology showed a ~ 1% decline of collagen in the skin per year starting at around age 20, so for most people collagen supplementation becomes more (not less) important as time goes on (1). We also tend to eat far less of the peptides and amino acids supplied by collagen than our hunter-gatherer ancestors did and we live much longer, making the need for a collagen boost that much more evident.
Collagen should be thought of as building material for your body, like a supply of bricks for the maintenance of a building's façade. As the façade is subjected to wear and tear, new bricks are needed to repair it. If there were to be an interruption in the supply of new bricks, this wear and tear would likely begin to show and the structure of the building may be affected, but this would not take anything away from past repairs. Similarly, if you provide your body with adequate levels of collagen for some time through supplementation and then stop, normal wear and tear would likely catch up to you if your collagen levels are depleted, but you're still better off than if you had never supplemented in the first place. A façade that hasn't been maintained for 5 years is in much better shape than one that hasn't been for 20 years.
References:
S, Shuster, Black, M, et al (1975). British Journal of Dermatology. The influence of age and sex on skin thickness, skin collagen and density.