Could a US citizen with a UK Long Term Family visa alternate 90 day periods in the UK and Switzerland indefinitely? Switzerland is a Schengen country, but the UK isn't.
Background: my mother in law is ready to retire. We live in Switzerland, her other daughter is in the UK. Our thought: she could spend 90 days here, 90 to 180 in the UK, then 90 here, or even alternate months.
Related: is there a Swiss equivalent to the Long Term Family visa that would simplify the process?
There is no rule in the corpus of UK immigration law that requires a given interval between visits, and no rule that restricts the number of visits a person can make.
Yes, as long as any of your visits to the UK are less than 6 months in duration, you can alternate back and forth for as long as your UK visa is valid AND at the beginning of each visit, you have a successful landing interview.
Your landing interview will cover Paragraph 41 of the rules, and in your case a special focus on sub-paragraph (ii).
Note: there is a lot of old internet lore on forums from an earlier era describing a 6-month-out-of-12 rule. Ignore it, Paragraph 41 is the sole controlling reference for family visitors.
Paragraph 41 of the rules was abolished last April, the links point to an archived copy. The current visitor rules are at Appendix V.
