Has anyone stayed longer than their application?

[domelro2]

Hi, I got my UK tourist visa to visit my fiance. When I applied I put for 10 days to spend New Years but I got the visa much later. Now I plan to just quit my job and visit for 3 months. I am a bit concerned immigration may ask me. Has anyone experience this? And should I just book my ticket for 1 month and change it later ? I plan to apply for the Spouse Visa next so super worried they might reject it if I stay longer than my application 10.0.0.0.1 192.168.1.254.