Visit Visa for Mom

Hi,
So my mom has been to the UK twice on 6 months visit visas and left as stated in application and her return flight schedule. Now I'd like her to visit again for a longer time. As we all know the process is cumbersome and expensive.

1. Can she apply directly for a 5 year visa and skip the 2 year visa as I'm not keen to keep going through the process of regular visa renewals for her.? Or is it best to follow the pattern of 6months, 2 years and 5 years?!

2. I can book a flight for her that shows she'll return after 5 months but worries that might impact her application. Advisable to book flight for return in a month and extend the return date after she comes into the UK?

Thanks alot for all your help