I have the impression that you may have remembered something incorrectly.
If you work in a EU/EEA/EFTA country, your accumulated pension benefits in that country stay in that country until you eventually retire. There may be some provisions for non-compulsory contributions like the Swiss 2nd pillar part that is not compulsory (Überobligatorium).
There are, however, two 5-year-limits that you may be referring to:
- Pillar 1 (AHV/AVS), where as a former Swiss resident with residence abroad outside EU/EEA you may buy up to 5 years into the AHV.
If you have moved to Switzerland from abroad and were never previously affiliated with a Swiss pension scheme, your maximum annual buy-in amount is limited to 20% of your insured salary for the first 5 years after joining a Swiss pension fund for the first time. (Source: German, Was tun bei Beitragslücken?)
- Pillar 2 (Pensionskasse, BVG), where as an foreigner moving into Switzerland during the first 5 years you can close a pension gap. Here, as far as I can see, there is no limitation on if you are an EU resident or not.
If you have moved to Switzerland from abroad and were never previously insured with a Swiss pension institution, you may make pension buy-ins up to a maximum of 20% of your insured salary per year during the first 5 years after your relocation. (Source: Einkauf in die Pensionskasse)
- In the 1st case, I don’t see any chance of you closing any gaps as this measure is intended for Swiss residents who move back from abroad. If you’re not sure, inquire with your cantonal SVA.
- In the 2nd case, you may be still eligible to do a bigger buy in than you would otherwise be allowed. It is best to check with your pension fund.
Otherwise, if I have misunderstood your question, you may want to more specific.