My speaker cables are very old, about 15 years. Of course they are Synergistic Research Element CTS, with Michael Spallone modified Tesla power, and I've only had them less than 3 years. Retail $7500 when new in 2005 mine were about $1100, including with the mods. Sound so good no plans to change them any time soon.
Cables really can make a big step forward. The CTS sure were. New Atmosphere are even better but at around $4k for a 2m IC not on the cards. Except I had a lot of old wire discarded over the years. With Synergistic, their Passport program gave me so much for trading those in it got me to Atmosphere Level III Euphoria without as you say breaking the bank.
The oldest continuous use in my system are a Synergistic Research Designers Reference .5 power cord, a Master Coupler, and Shunyata Powersnakes Cobra. Oh, and two Electraglide Fat Boys. All from around 1993.