I'd go for a 5 year motor. Getting the meter installed is a pain in the arse and costs money. Door stickers cost money. Initial suitability costs money. Meter sealing costs money. Time off the road costs money. Seat covers cost money. If you're OCD the first year's motor tax costs time as you'll want the disc as soon as your passed out so you'll have to travel up to Dublin to buy it in person, etc, etc...
Add in trawling the net to find the car you want, negotiating the deal, signing the deal, arranging motorloan, changing insurance, changing taxi portal thing, changing car on the various Apps (MyTaxi, Uber, Etc), transfer all your personal taxi bits and bobs and all the safety equipment to the nua cab.
Jaysus ! I couldn't be doing all that every Two years, I've a pain in me head already just thinking about it !