Watched a young guy going the side kicks in Koryo tonight, quick as quick could be. Puts my effort to shame, only consolation I can claim is that I taught him  lol

I'd like to get my kicks to a lot faster specially the double kicks. I understand its a bit tough for someone my age to be able to perform as I could 30 plus years ago but would still like to have a shot.

A question for those approaching grandparent status. What do you do to maintain and improve your speed in your kicks. Any advice would be great

for that particular kick in question, i find working it backwards helps a lot.  instead of doing mid side kick, re-chamber, and high side kick, try just doing high side kick from chambered position, but not in a fluent motion (so that you don't use momentum for the high kick).  practice with your front leg first, so you are chambering with your front leg, wait for half a second or so, and try to do a high side kick.  once you get comfortable with that, then extend your leg so that it's in mid side kick position, chamber and do the high side kick.  you don't have to hold the mid side kick, but it would be easier to just place your foot on a table or something in mid side kick position. 
it's the chambering from mid kick and then kicking high that messes up momentum and balance, which require a lot of core strength.  and working it backwards can help you out at the very beginning.  of course, once you get used to doing mid/high side kicks, you have to do it the proper way till you get used to it. 

Try these exercises.

   Get two paddles. Then have someone hold one out waist high. Then do round kicks to the paddles as fast as you can. Do this for a minute straight. Then switch legs and repeat. After doing each leg once have them hold both paddles out waist high and alternate legs for about minute. Practice this often and you will improve speed. Be sure to have them count you kicks. I'm up to 400 kicks in three minutes.
    Another is get two paddles. Have someone hold them close to there chest. You face them in fighting stance.  On there own count they quickly hold one of the two paddles out. Kick the paddle real fast. Then the holder pulls the paddle back towards them.  Have the holder mix it up, move around, hold the paddle for various kicks. 
   Some competators appear to be fast, but are not real fast its just there reaction time to launch a kick is higher than the other competator.

i understand age wise that there are diffrences but there is no doubt that leg weights can help at any time.  i got my self 20lbs leg weights from a friend and by just walking around the school with them(8hr short distance for walks) my speed has increased dramatically.  if u use short burst of diffrnet kicks everyday with even 2.5lbs leg weights i garantee that your speed will increase dramatically like mine did.  that or you could push your car for 100 meters up a hill to work out your calfs.  either work ive tried them both and if you do them both you will feel like a pile of doodoo afterwords and the next day light footed like never before.  my point is that any leg excersise driven to the extreme for at least two days will increase spedd.  it did for me.  (if i were you i would start off with leg weights and if you choose follow the other exercises or make your own...)  hope it helps.

very good point about wrist/ankle weights. 

when training with wrist/ankle weights, you only should practice on heavy bag, not paddles.  and the bag is not the target, but the impact point should be about 3/4 way of the range, so that bag can slow down your kick or punch before you fully extend your legs/arms. 
the safer way to use wrist/ankle weights is to do techniques slowly.  kicking slowly even without weights can improve your techniques, and doing it with weights will help you get over the plateau.  and doing patterns slowly with weights on wrists (or even with 5-10 lb dumbbells in hands - will have to do all hand moves closed, i.e., substitue hand knife techniques with fists in order to hold dumbbells) can help you with endurance and strength in general.