Potential life of daily driver

Mechanic is installing another engine 110,000 because he didn’t insert plug properly, all of the engine drained out. How many miles can I expect from this [Subaru] engine?

Original engine had 175,000 miles.

Drive average 550 miles per week.

It’s 1995, auto transmission.

Well, if you’re saying this current engine has 110k miles no one will know how long it will last because no one knows the history of that engine (including the guy putting it in) or what your driving and maintenance habits are.

Consider this. He’s apparently installing a high mileaage engine with an unknown history.
Did he perform the following procedures before installing this engine?
New rear main seal.
New transmission front pump seal.
New timing belt, water pump, and tensioners?

If the answer is no to those questions then he has screwed up yet again and ideally a compression test should be run before a used engine is installed.

Did your engine have the head gaskets replaced during its lifetime? Hopefully the donor engine has had the same if so, as you may re-experience this repair.