This is what I do but the answer for OP may depend on which countries OP plans to travel to.

When I retired, I lost my AT&T iphone. Now I'm retired, I use the phone rarely except, when I travel (mostly to Europe), I want a phone that allows me to use the maps, check transit times etc.. Where I live in the US, T-Mobile is unreliable. I use a combination of:
a) red pocket when I am in the US (runs on the AT&T network): this doesn't work at all outside the US
b) vodafone UK pay-as-you-go when I am in the UK or other countries (mostly Europe) where buying a vodafone roaming plan costs less than buying a local sim
c) buying a local sim upon arrival

If I don't travel to Europe for three months, I keep my vodafone number alive by sending a text from my UK vodafone number to my US red pocket number. There's no monthly or annual charge for vodafone UK pay as you go.

For me, google fi would be more convenient because I could give everyone (eg. hotels and airlines) a single phone number that I know will always work no matter which country I am in. However, I can't justify the extra cost purely for those very rare times when a hotel or airline want to call me urgently and don't have the correct phone number for the country I am in.