I just got back into climbing after a 6 year hiatus while living in Austin. Though I had fairly new ropes that were well maintained before I moved, I wasn't sure if sitting for 6 years (in a rope bag) in 900 % humidity was ok to climb on. My thought was, "there is only one way to find out" and I wasn't willing to risk it. Sadly, I ditched both ropes.
Recently a friend was going through something similar and this lead to our question: Is there a way to test you ropes? What is your baseline for rope replacement? Thanks!
If you haven't found Black Diamond's Quailty lab, enough the next few hours. They did a test on old ropes a while back.
If you look at manufacturer they give you a lifetime suggestion based upon use for all soft gear.
Back to personal opinion, I agree. If you don't trust it, don't use it. However, I've eeked out a few more months and years from rope by doing an inspection and then having a friend do an inspection and talking about it. At very least you can demote this rope to top rope only for when you have friends.
After working at a climbing gym for years, we would constantly check our ropes by checking for fraying, dead spots and the thickness/swelling of the rope. With that being said, I've always been told a rope for outdoors has about a 5-7 year life span depending on a few factors including (but not limited to) how many heavy or big falls have been taken on the rope, storage placement (home, garage, car etc.), and the frequent use of the rope. I've had my rope for 5+ years but it wasn't used frequently outdoors, stored in a rope bag and kept inside my house (not in hot temperatures). I have checked my rope for dead spots, fraying, or swelling of the core but it's been good so far. I would recommend flaking out the rope and hand inspecting it for any suspicious feeling (a bit tedious but worth it before getting rid of it). I hope this helps!