Personally I take a fix for budget certainty. In hindsight I could stitch together where interest rates are/were and when would have been absolutely ideal to fix, for what duration, or to stay out to avail of a better rate, and optimise my mortgage lifetime interest bills. Just like I could look at when I should have ideally bought and sold Nvidia or Apple stock. But I'm also trying to budget for a household and generally avoid risk on my dwelling.
I wouldn't fix for a long time at a very high rate. I'd bet that it might come down over 1-2 years and taking a shorter fix. But neither would I stay out on a variable for a long time to wait for a few more ECB cuts to come through - recall the start of last year when the markets priced in a lot more interest rate cuts at the start of the year than actually happened.
Looking at the market right now (and obviously the products available will depend on your circumstances) you can get 3% on a 3-4 year fix with AIB (green mortgage) and PTSB (doesn't seem to be "green" required). ECB is at 2.5%. Could be headed for 2% over the next few quarters before the tariff stuff kicked off. At retail that probably means 2.5% mortgages might be on the cards by some stage in Q4. But then the tariff stuff could drive things in another direction.
Say you had a €300k mortgage with a term of 30 years, and went on to a fix now at 3% vs gambling for a 2.5% fix in 9 months time. Your monthly minimum repayments would be €79 more expensive per month at 3% vs 2.5%, about €3,792 over a 4 year fix.
What would it cost to sit on a variable rate for 9 months to see if the rate came down? Depending on LTV, you'll get about 3.75% to 3.95% on the market. Vs a 3% fix now, you'd pay between €127-€158 per month more, or €1,143-€1,422 over 9 months, to stay out variable and see if you can get a 2.5% fix. That's about 30-37% of your potential saving over a 4 year fix at 2.5% vs 3% gambled on the idea that rates will fall, within the timeframe you've set out. Makes waiting look that bit less attractive.
Again, this is a scenario with limited knowledge of your situation.
Personally I'd consider 3% a pretty fair and ok rate, affordable, not a million miles off where the bottom of retail interest rates have been available for anyone not on a legacy tracker, and I'd fix there happily today, in full knowledge that I could be leaving money on the table.