I think for at least two more seasons he will perform at his current level, and then you can think about ending his career. Especially when you come to a club like this you just have to show a good game and I am sure Robert understands that and will do everything to keep the bar high. Also, he may not be going to Barcelona
Yes you are right, at the moment he can still show his best game for at least two more seasons. Of course, this time of maturity will be used to help them win a title that has been difficult for them for several seasons. Of course the coach will not arbitrarily recruit players if the player is judged to be unable to contribute.
Lewandowski can make a good contribution. Yes, if you say he played well in Germany you can say "Spain is a different football", but Robert also played well in the Champions League and scored many goals, so for him it does not matter in which league and against which team to play, he can adapt in Barcelona