Oil Change Questions

vtec to vvel

I've been many searches on both this forum and Google, but couldn't find a straight answer and the threads always seem go off track pretty quickly. This isn't a conventional vs synthetic oil thread, but rather had a few quick questions.

Background: I bought my 09 approx. 3 years ago with 50k miles on and have been using synthetic blend. The past 2 years, I found a job to where it's take me 3 minutes to walk, so I just leave my car in the garage. The first year, I put a shitload of miles, but the past 2, I've put maybe 4k miles each year, and don't really drive my car. I'll still change out the oil once every 6 months even if I don't hit the 5k mark. Today, I went to go buy my usual brand of the synthetic blend, but turns out it's discontinued (?) and replaced with oil with full synthetic.

My questions are:

1. there is currently approx. 74k miles on the car. I've been using the synthetic blend (yeah i know it's prob mostly conventional) up until today. I understand that oil itself does not cause leaks, but rather worn seals, but my car does not leak whatsoever. Changing to full synthentic at 74k miles, is the car too old to go full synthetic?

2. the likelihood of an oil leak?

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