So, we should also think about how we might like to start this change. One way we could fairly start it is say that at some block in the future the new regime forks in, then for the next year, there is no change to your pay, since no Mnode has been active for more than a year since the start of the change. Once the first year is up and some mnodes are now more than a year old and qualify for the bonus, the new pay schedule kicks into gear, dropping the pay of nodes <1 year old to 0.8 of what they were getting and distributing the 20% extra equally among the nodes that were active for the whole year.
After two years, the next change happens, however, it only affects the long running nodes. Now, nodes active consistently for 2 years will get a bonus above the nodes running for only over 1 year. Nodes having run for less than a year still get just 0.8 of what they were getting before.
etc until there are nodes running 6+ and all the tiers have some active nodes in them.