How many eggs do you want? Hens will still lay eggs after 4 years. They don't suddenly stop all at once. Sometimes even 8year old hens lay eggs. It's just not very many eggs. If you don't use many eggs though then you might continue to be fine for awhile. Personally I find 6years of having a chicken to be quite a long time for me and the chicken. Most likely something will happen in that time to either end their life or allow you to keep them. You do have to plan just in case but I wouldn't let that stop me from having chickens at all.
3 chickens really isn't much work. You can make it into a ton of work by constantly cleaning everything but do they really truly need it? Go count how many people on here use the deep litter method where they never remove bedding from their coop but only stir, add more bedding, and clean out extra poop covered areas like roosts and boards near roosts. I follow the old standard for farms around here. Clean it good in the fall, bed it deep, clean it good in the spring, bed it light for the few months of summer, and leave it alone the rest of the year except to add a little bedding as needed. My coop never smells. Provided the coop is big enough and stays dry it should not smell. You may need to clean a little more often and spend a day every couple weeks scraping down areas that get extra poop since you are in town but constant spot cleaning is not necessary. Neither is scrubbing waterers several times a day or even every day. Sure you can but whether it's necessary is highly debateable and most likely not followed by a good majority. I check mine daily and about once or twice a week dump one in a stock tank to soak and grab a clean one. Then I rinse it good the next day and leave to dry. They get fully disinfected maybe monthly if I remember. My chick waterers I disinfect more frequently but I really don't find it necessary for the adults. A little algae won't harm them either so long as it's the green kind. One of my low stock tanks doesn't get emptied all summer, grows a nice crop of algae, and gets filled with guppies to eat the mosquito larvae. They drink out of it daily. No sick chickens so far. For the ones in the coop I lost count how many I have and I spend maybe 30mins a day actually taking care of them including opening the door in the morning and closing it at night, about one day a month doing extra cleaning, and a couple days spring and fall emptying and refilling the coop. It's my seramas and chicks in pens on the porch or brooders in the house that take up my time.
