Records were filed according to date of discharge. In theory records up to the end of 1913 are with Findmypast. Records for men discharged 1st January 1914 to (August?) 1920 are with Ancestry. Discharge came after any time in the Army Reserve.
You need to read the records to see if there was a break in service. Sometimes they carried on with the first set of records even after a break.
As Ady there is also a chance of misfiling. I once came across a 60-day emergency enlistment from the 1920s in with pre WW1 records.
Ken