Which is the best option in terms of fixation? That's possibly less clear cut and it really comes down to your own preferences and risk tolerances, and the outlook for interest rates.
The higher the debt burden the more sensitive your financial position will be to fluctuations in interest rates. It means you will likely have less scope to absorb an interest rate hike. In such a situation I would say fix for longer. It's also worth considering personal circumstances. Are there upcoming changes in your life that you might appreciate the certainty that a fixed rate brings.
In contrast if your debt burden is already low or say you expect a promotion in the short term (or perhaps your husband has recently invested in a rather profitable car wash business ;-) ...) or you've an ongoing expense you expect will stop soon (e.g., crèche fees) - it might make sense to fix for a shorter period and reassess your finances at that stage. Also worth noting we are very close if not at the top of the rate cycle. The ECB is expected to cut policy rates in 2024. However, I'd argue these cut(s) and the associated changes in longer term market rates may not get passed on to Irish borrowers any time soon. Our banks already have very low funding costs (our deposits) and also the Irish mortgage market is perhaps less competitive than other countries.