>>mattjh+(OP)
What often baffles me with engineers and especially engineering managers is that they don't derive the estimates from metrics of prior projects, especially for long running teams (as opposed to project teams). You don't need to estimate down to the minute, but you already know how many tickets/work items the completes at a given time interval with how many people in the team etc. This should give a rough estimate of how long a project might take, and you can confidence intervals like 90% confidence we finish this in 3 months, 70% confidence we finish it in 10 weeks, 50% confidence in 6 weeks and 10% confidence we finish it in 2 weeks.
IMO this is also a better way to communicate with stakeholders outside the team instead of committing to a specific date. It gives more context and clearly communicates that this is a probability game after all since there are quite few moving variables.