'Is' or 'has been'

[subhajit123]

'Is' or 'has been' : Which one should I use?

'John is a very good person. He is/has been at his best when comes to help people for quite a long time now.'

 

[Rover_KE]

'John is a very good person. He has been at his best when it comes to helping people for quite a long time now.'

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