Fast enough to meet yourself coming back 
Current Sag A* unlimited record is 2 hours 45 minutes (https://forums.frontier.co.uk/showt...esents-The-A*-Challenge?p=5313205#post5313205). 140 jumps in total. Lots of time lost on that run to silly mistakes and it wasn't a fully optimised loadout as I was using my explorer ship with ADS, DSS, shields and SRV so it could have been somewhat faster. Since I did that run we've got lightweight sensors which adds another 6+ LY to my ship and it should be possible to get down to something close to 2 hours 15 minutes.Before Neutron Start Jumping, Engineers or Jumponium were a thing the record for Sag A was about 8 hours. With those 3 things it's way way lower. The OP's post is impressive but not beyond belief.
EDIT
144 Jumps! My commander in a fully laden Cutter that's heading for Colonia right now can only dream of such figures, that's about 3 K LY's for me.
You can't possibly do neutron jumps in 45 seconds and an average of 65 seconds would be really good (I averaged 67.7 seconds on my Sag A* run). Also you need to make refuelling stops which can take some time and the jump from that system isn't going to be neutron boosted unless you happened to find a NS system with a scoopable star sufficiently close to it. Also need to stop and repair the FSD every 15 or so boosts.If you hit it perfectly, got the neutron boost every single time with max range, you can do it in [21800 LYs to Colonia] / [Jump Range x 4] = number of jumps, [number of jumps x .75 minutes per jump ], is about 1 hour and 15 minutes theoretical perfect time.
I suppose jumping from neutron to neutron isn't possible right? Cos of fuel scooping.
Elite Dangerous Neutron Router https://forums.frontier.co.uk/showthread.php/308674-Neutron-Highway-long-range-route-planner
Yes, it is possible and that's what most people do when neutron surfing. Start with a full tank, keep jumping neutron to neutron until your tank needs a refill.Mind you, more often than not you'll find a gap that you can't quite cross without using another star type, and that can work out as a fuel-stop.
Current Sag A* unlimited record is 2 hours 45 minutes (https://forums.frontier.co.uk/showt...esents-The-A*-Challenge?p=5313205#post5313205). 140 jumps in total. Lots of time lost on that run to silly mistakes and it wasn't a fully optimised loadout as I was using my explorer ship with ADS, DSS, shields and SRV so it could have been somewhat faster. Since I did that run we've got lightweight sensors which adds another 6+ LY to my ship and it should be possible to get down to something close to 2 hours 15 minutes.
You can't possibly do neutron jumps in 45 seconds and an average of 65 seconds would be really good (I averaged 67.7 seconds on my Sag A* run). Also you need to make refuelling stops which can take some time and the jump from that system isn't going to be neutron boosted unless you happened to find a NS system with a scoopable star sufficiently close to it. Also need to stop and repair the FSD every 15 or so boosts.
Respect and congrats. Now thats a record hard to beat.
I went with 32+32 which seemed about right. I might try and run some simulations before my next run to see if there is a better amount, but as long as jump ranges keep increasing with every update there doesn't seem too much point in trying to optimise things to the nth degree.Allitnil - what tankage do you use? All those stops for fuel add up. I used 32T+16T but I feel 32+32 (or more?) might be better in terms of ly/h.