@ReleasePT - whilst each member state can be more restrictive, I do not believe they have given you the correct advice so far.
As I mentioned before, the ME-IR just allows you to fly in IFR conditions on any aircraft type that you currently have an active rating on. This rating could be on absolutely anything; MEP or A340 or A320 or B737 or B747 or ..... You get what I am saying here... The 2 ratings are very different, and so their validity will be unrelated.
If you don't want to fly a twin piston aircraft, why would anyone be forced to keep renewing their rating for it?! It makes no sense, and the licensing authorities know this.
To put this in context, it is also a requirement to have a Class One Medical certificate to fly commercially, however the validity of your CPL is 5 years, whereas your medical is 12 monthly.... Using the same logic as your licensing authority have applied thus far, they might aswell tell you that your CPL must expire on the same date as your medical. This is just silly!
Good luck and keep us posted!