If you hold an SP IR then the last time you passed the test in an aircraft will also
count as the test for an IMC / IR(R) and you can apply for an IR(R) on the basis
of this pass valid for 25 months from the date of test.
However you say you hold an ATPL which implies you have an MP IR.
In which case take the Test!
This makes good sense - No matter how qualified and experienced you are
in flying IFR and IMC Approaches in Controlled Airspace in a Multi Crew
enviroment with an aircraft with all the kit - including IFR approved GPS.
This is not the same as flying IMC Single Pilot in Class G in (say) a very basically
equipped PA28 followed by a Procedural Approach in to a non-radar airfield.
Skills are different and hence need to be separately assessed