God has always existed.
If you intend to bring up infinite regress, it won't work.
You are interpreting reality in terms of mathematics, which isn't against the rules in all cases but will get you into trouble if you take it beyond what is reasonable.
Just as you want to suggest that there hasn't been enough time pass for an eternity to have elapsed, Zeno suggested that motion itself was impossible for the exact same reason.
The inescapable facts are that we both move in refutation of Zeno's paradoxes and that we do so in the present in refutation of the infinite regress paradox.
The key thing to grasp here is the difference between a paradox and a contradiction. And there is a difference. If there weren't, knowledge itself would be impossible and you'd not be able to read this sentence. In other words, if the logic and all the included assumptions in the infinite regress argument are correct, we don't exist (yet). The fact that the argument is made is proof that we do exist, therefore there is something about the argument and/or the assumptions made in it that is in error. Whether we are able to figure out the error is not relevant. This is the essence of all paradoxes.
Contradictions, on the other hand, are somewhat different. A contradiction is a single statement that contradicts itself, whether explicitly or implicitly. In the case of timeless existence it is implicit. The self-contradiction is found in the concepts upon which the terms used are predicated. Timeless existence uses one concept while denying a concept upon which the used concept is logically based. It's akin to saying something like, "Martin Luther King Jr's father never existed." It can't work. Likewise, discussing existence outside of duration is a self-stullifying thing to do. And make no mistake, that is precisely what you are doing by bringing timeless existence because as it is not possible to discuss existence without duration and impossible to discuss duration without time. Your every comment on the subject will be a contradiction. You've lost any debate on the topic by having brought it up!
Here's the punch line...
To accept that God exists outside of time in order to resolve the infinite regress problem is to accept a contradiction as the solution to a paradox.
You might want to rethink that.
Resting in Him,
Clete
Stolen Concept Fallacy