Years ago I saw a Blondie comic strip where a salesman was trying to sell half a new roof to Dagwood. Dagwood asked how long it would take for the new shingles to weather-in to match the old shingles, and the salesman said, "About as long until the other half of your roof needs to be re-shingled."
Since you are asking strangers for answers to your question, and not providing any relevant info, IMO it doesn't matter if all four mounts are the same age or a year apart.
Well, it would matter if you are using really crap mounts, so keep that in mind.