We both work full time so cosleeping was sometimes the only "together" time we had as a family, so we were happy to keep doing it. Then when DD was about 3 she started wanting to sleep in her own bed some nights, and this gradually increased until she was happy to sleep in there every night.
The plus side of the long term strategy is that she is happy to take herself to bed at 7.00 p.m. every evening, goes straight to sleep and sleeps through until late at weekends, because that is the behaviour she has learned by our cosleeping in the formative years.