I'm in a very similar situation that you were in: I'm on Verizon with 3 lines, 1 of them grandfathered into unlimited data. Over several years the monthly bill has crept up to $230-$250.
Since it went up slowly I never thought much about it, until I reviewed last year's finances and realized what had happened.
Do it. T-Mobile is great. And they will pay your ETFs.
Customer service is great. I recently had a billing mishap (their end, ended up $30 over) and to make it up to me, they discounted my account by $30/month for a yr. This is magical compared to the shitty customer service with Sprint and Version.
Since it went up slowly I never thought much about it, until I reviewed last year's finances and realized what had happened.
T-Mobile is looking very enticing.