Bought mono blocks, now spkr cables too long

Since electricity travels at nearly the speed of light. Its exact value is defined as 299,792,458 metres per second (approximately 300000 km/s, or 186000 mi/s). The only reason to shorten the cable is cosmetic. If you decide to go that route, hopefully, you can sell to someone else after you compare and keep the one you like the best. 

@noromance with respect to a home audio system there is no length that could be considered too long. Sound and/or data is transmitted instantaneously. That's why you experience no delay when talking on the phone with someone across town or working on laptop sharing data on a zoom meeting with co-workers several states away.....etc. The speed of light is so freaking fast it is hard for most to comprehend. The signal can travel around the earth 7.75 times per second. Bet you can't measure a difference unless the cable has unusually high impedance. Doubtful if under 30 feet, in which case I feel very sorry for your wallet 😬