IFRS 15 change of period of recognition of up-front fee

[PIOTRB]

Hi, we plan to change period of recognition of up-front/activation fee (for all contract we spread such fee over estimated expected period) and I have some questions:
1. Is it regulated by IFRS 15 (any kind of contract modification) or IAS 8 (as change of estimate)?
2. Can such change be made during a year, e.g. starting from May or should it be made starting from January even if it the decision is made in May?
3. Should such change be made prospectively?
Thanks

[JRSB]

Why are you changing it

[PIOTRB]

Currently we assess that our relalionship with customers on average will be shorter than previously estimated

[Marek Muc]

Are these fees treated as separate performance obligations? If they aren't, how do you recognise revenue for the performance obligations that include these fees?

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