Adjust Pastor's Salary Based on Years of Service?

We don't do years of service increases but with all our staff we do a cost of living rounded up to provide a minimal increase but to still keep the salaries for the positions at "market" levels.  We are currently exploring the possibility of having bonuses at milestone years, like 5, 10, and 15 -- something in the line of 3% of salary as a bonus that year.  That would not factor into regular cost of living increases and so would not inordinately inflate salaries.  Not sure how this sounds to you or if anyone has incorporated something along this line or otherwise.  Any feedback is certainly appreciated!

My experience is much the same as Ray's explanation below.  There is a cost of living increase of 1.5%, or whatever the stats say.  And I have usually had some sort of a salary conversation with my elder or somebody from council before the new budget is presented.  When my life situation changed (when I married, when my children started Christian School) there were additional conversations.    But there's no one size fits all approach that I've found.  

Thank you this was very helpful.