Can't comment specifically on Mini leather, but if it's sourced from the same place as 3-series BMW leather, then I wasn't impressed with that in my 320D (2010-2013).
Despite me knowing how to look after leather and feeding it regularly, it went all baggy on the squabs after only 36000 miles.
I hate seeing baggy leather seats.
An upholsterer could maybe fix baginess though, but it's a hassle and expense.
And if a £1500 sofa can go for 10 years without the leather going baggy, how come £1500 BMW leather goes baggy after three years??