I recently bowled with some old friends and neither of them had a ball newer than 2008, but the balls they mainly used were from late 90's, early 00's.  This is on older wood lanes, so needing hook in a box certainly isn't necessary.  Both were effective and averaged about as much as they thought they should. 

I told one of the guys that if he had a couple newer balls, bowled on wide open house shots, and believed it possible, that he would average 25-30 pins more than he was.  A new house opens in his hometown soon, so we'll see.

In a roundabout way, I'm trying to say that you have to ask yourself what you want/expect out of your bowling game now.  If you are bowling once a week with a few tournaments you aren't expecting to win, then your equipment is likely the best matchup since you can predict their reactions.  Newer equipment has potential for more hook and hitting power, but you may not like the reaction shape as they will likely be sharper than your current stuff.  If your situation changes, then you will need newer equipment to keep pace with the leaders.

I've asked a few pro shop guys about older balls sitting and they all agreed that they should still be good provided the core doesn't settle.  We've all seen balls crack.

It has now been several years since I bowled a league or even darkened the doors of a center for a few games with an office party...but...that being said, I would have no qualms about continuing to use older equipment.  Sure the shape may not be one that crosses a ton of boards, but the older stuff will still work. 

The last office party we had, I took in a tote with a Sonic X and a Pearl Assault along with a second tote that had a Gold Grenade (polished urethane) and an old Roto RH (the Roto version of the Yellow Dot bleeder).  I had looks to the pocket with all of them.

I bought a Columbia Power Surge when it was issued in 1999 and used it for nearly 10 years. I cleaned the ball at the lanes after nearly every series and resurfaced the ball once. The Surge's reaction was still pretty good after many, many games. With that neon purple coverstock, it also looked great turning the corner. I retired the Surge mainly because it was 16 lbs., and I was moving to 15 lbs. But it was one helluva ball in its prime.

It really depends on what you are looking for in the ball.  Most disappointing balls are those that guys buy as hook monster with a lot of surface.  They lose reaction quickly and I have always found it difficult to maintain or return such balls to box condition.  This was an issue even back in the urethane era where strong balls often came at 500 grit box condition. Those urethanes also soaked up oil, and the oil penetration made it difficult to return those balls to their performance out of the box   

Balls that are bought primarily for house conditions can last a long time if you aren't looking for a super aggressive surface, which is really not necessary anyway on house shots. 

For some reason I find my older stuff on a house shot works the best.

I have a Brunswick Diamond Back I polished a few years ago I shot 300, 3rd week of the season with it this year. I also have a Lane 1 Enriched Uranium. Mid season I brought that back out and had six week straight weeks nothing under 700 with a 795 and 96 clean in a row with an ave of 248 during that time. When I buy new stuff it is for my Sport league and tournaments. I clean them after each use and resurface after 30-50 games and try and extract the oil also.  So I keep going back to my old stuff when ever I get in a slump and for some reason it gets me out of it.

I think both ball are between 8-10 years old & the lane 1 has over 500 games on it

Just my .02

One of my most favorite balls ever is my Clutch Pearl, which is 6 years old? Love it so much I am sitting on a nib one just in case! Still works just fine.

I bowl with two Dynothane Vendettas (original and particle). Bought them in 2004/2005 and some of the most reliable and snappy equipment I have.

I maintain them religiously with our products to protect them from ball death. The next few sandings the originals serial will be removed so I need to get that engraved back into the coverstock.