If you are pretty good with not losing your gear, and don't beat it up like a spoiled 12 year old, then the price of a good pair of sunglasses is well worth it. I've had the same 580G for 4 years now. I've fished just about every weekend if not every other weekend, and started tournament fishing last year, and they've held up well. With the investment put into a good pair of glasses, I've had a lanyard on mine since the day I bought them, as I could not fathom watching a pair of $200 + pair of glasses sink to the bottom of a lake.
Once you get them, you will kick yourself for not getting them sooner, as they can make your time much more enjoyable on the water, than what you ever could have imagined. You will be able to see things better, and I can say this for me, my eyes are not as fatigued as they used to get.