Do you have a clear idea of how much new REP will be created, relative to the existing supply, each year?
The only time REP is minted is during a fork. The amount minted in this case is 5% (subject to change) for anyone who participates in choosing a fork during the forking window (60 days, subject to change).
This means that as a holder, as long as you participate actively during a fork then your REP value will never be inflated, at worst your position remains the same if everyone participates. If some people don't participate, then REP can be seen as deflationary from your point of view which means your position strengthens.
Keep in mind that during a fork, anyone who migrates REP to a universe different from yours is deflating REP supply in the universe you choose. This is further deflationary.
If no fork occurs (if everything is running smoothly forks should never happen) then there will never be any more REP minted.
TL;DR: The only time REP can inflate from your point of view (meaning your REP loses value due to minting) is if a fork happens and you do not participate. In all other scenarios REP is either stable or deflationary from your point of view.