The ships are always receiving repairs, upgrades and replacements in order to house the large population. Each individual ship tends to fall under one of three specialization classes; liveships, lab ships and homeships. Quarians generally live on the ship that they work on, as commuting from one ship to another is seen as an unnecessary waste of resources.
Quarians, on most ships, will stay in their protective suits. On rare occasions (for medical or reproductive reasons) they will meet up on "clean ships". On these ships they will remove their suits, even though they are sure to suffer from allergic reactions or infection due to each others presence.
Whenever the Migrant Fleet nears a planet, the quarians essentially strip mine it for resources. This has caused many to feel a sort of animosity towards them, and some go as far as offering them ships or resources to make them go away.