When to switch to T-Mobile?

Been on Verizon for years, never switched. Have 2 fully paid off phones on my current plan. I’d like to take advantage of an iPhone 18 pro deal when switching. Would it be best to switch when the pre-orders come out on the 12th or wait until after the actual release day? I see $930 off an 18 Pro with Experience More 2.0, which is probably the plan we’d go with. Do the deals typically get better after release day or should we do this deal with the pre-order? Any additional advice is appreciated.