The only limit you have to your length of stay is the total number of points you have to use to reserve a stay at a DVC resort. There are two partial limitations which actually do not limit your total potential stay time: (a) at exactly 11 months out from day of arrival (or 7 months for non-home resort), you can reserve up to 7 nights maximum, but you can then call later and add nights (the rule is effectively that your departure date from WDW can never be more than 11 (or 7) months plus 7 days from the date you call or go online to reserve); (b) if you attempt to reserve online (even well beyond the reservation window), you will be able to reserve a maximum of 30 days (that is a computer system not rule limitation and you can call and add more days; that was previously 14 days until they improved the computer systems).
As to any concerns raising issues of residency if you stay a very long time, be aware the official DVC documents prohibit you from using any stays at a DVC resort to establish residency and, in Florida, that legally prevents one from making any claim of residency based on time spent at a DVC resort. Moroever, there is no "tenancy" limitation requiring any formal eviction proceedings if you stay for a long time. In Florida, the police, upon request of the resort operator, can forcibly remove a guest from a room without any formal court proceedings.