I've posted about this earlier, so apologies if some of it is repetitive.
Here's the exact situation-
My mum has been visiting me in the UK for about 3 years now with no issues. Never had an application refused, never used public funds and never tried to work in the UK.
She has never visited me for longer than 2 months at a go until now. She came over in February this year on a 6 month multiple entry tourist visa and the initial plan was for her to stay with me for only 3 weeks (and this is what was stated on the application). However, my circumstances have changed in that I've had to move etc. and I'd really want her to stay on till the end of April to help me through this.
Given that her visa is valid until August and there is no restriction on it that requires her to leave within a specified number of days, it shouldn't be a problem.
However, I am concerned about her next visa application. She might visit me very briefly in October for my birthday and for this she will have to apply for a new visitor visa (her existing one expires in August).
Will it count against her that she already stayed here for around 3 months this year? And will it look dodgy that she initially said she'd stay for 3 weeks but ended up extending it?
Her previous visit was back in 2012 and was just for 10 days. She didn't visit all of 2013.
She always shows she can support herself, she owns property back home, she is self employed so it's OK for her to be away for 2-3 months, and always travels with a return ticket (which on this occasion is being extended).