Quicken Loans is NOT a low cost lender. You can do better.
Your best bet is to shop the loan locally and see if you can come up with a no-cost or very low cost option if getting the rate down at minimum cost is important to you. If a lender pays for your closing costs and you get a "no cost" refinance, it's usually because they are being paid by the investor that buys the loan for a locking you into a higher interest rate. The company that gives you the loan will turn around and sell the loan to an investor, and they get a premium for the higher rate.
An ethical originator will use most of that premium to offer you a competitive deal on costs. Less ethical originators keep most of the spread for themselves. That's why it's important to get multiple loan quotes. That's how you figure out who is more on your side in the deal. You can also find out what the "cost" of a lower rate is by asking how much the rate is reduced for one or two points versus no points.
Knowing your credit score before you start the process is important. Pricing is score dependent, and can vary dramatically if you are on one side or the other of a cut-off point.
In your shoes, unless I already had the pay-off cash in hand, I would increase my flexibility by going for a longer term with a fixed rate. That way, if things changed before the scheduled pay-off, you would not be stuck in an adjustable rate product at the end of the lock period. You should be able to get your interest rate down into the mid-threes at a low cost for 15 years and retain your options.