Strictly speaking, under Revenue rules you are not supposed to invest AVC’s in anticipation of retiring early. The ability to pay AVC’s is supposed to be based on the likelihood of a difference between the eventual Main Scheme benefits and the Revenue maximum at Normal Retirement Age.
However it is not unknown (common) for individuals to invest AVC’s in anticipation of actually retiring early. However assuming one does retire early it needs to be borne in mind that whilst the Main Scheme benefits will be reduced, so too will the Revenue maximum.
For Public Servants in the old DB Scheme it should be relatively easy to estimate if there will be a shortfall at NRA. This will facilitate AVC’s. For members of the post 1995 Integrated Scheme , there should be plenty of scope (even with full service) since one can use AVC’s to add back the State Pension (currently circa €13,000 pa ) which could have a capital value of c€300,000. For members of the newer post 2013 hybrid scheme, the calculation is much more complicated, but likely to be plenty of scope for AVC’s.
The essential point I would make is that it is pointless deliberately overfunding. Your unlikely to be able to use any excess funding at retirement (it cannot be taken as a taxable lump sum, it cannot be transferred to an ARF). That said it is very rare in my experience to see someone overfunding due to AVC’s. In general I see little point in paying AVC’s in one’s 30’s (accelerate mortgage payments instead) but as one moves into ones 40’s and 50’s then one should begin to focus more on the financial aspects of retirement.
The whole area is complicated and ideally individuals should get professional advice. But just investing AVC’s to benefit from tax relief is going about it the wrong way.