Hmm yes, good points.

It might be better expressed as total fees for a block (for example > 10 BTC), and you'd have to do it across some span of time in case there's an odd software bug (I think recently someone accidently set a +90 BTC fee).

Perhaps something like this: Within the next 4 years, there will be an 8 hour period where every block mined will have +10 BTC fee revenue.