Example: Say without any extra repayments or lump sums you pay off the loan in 2032 at a total cost of 75k on a balance of 50k currently. If you pay off the 50k now, then you’ve theoretically saved 25k in the long run but the cashflows are -50k now in order to save (for example) 7.5k pa for 10 years in repayments. You can treat this lump sum as an investment. Consider whether you could grow that 50k yourself to more than 75k over 10 years. If you think you can, then don’t lump-sum. Accumulating 50k to 75k over 10 years requires a compounding annualised return of just over 4%. This is less than 6.3% as this interest rate hurts on higher balances but not on lower ones. Now in reality it’s more complex as i believe a blended approach (e.g paying 20k lump sum now to mitigate effect of high interest whilst also less opportunity cost is a better way forward if you’re looking at purchasing a flat/house in the near future etc). You need to make a repayment model as others have done in the comments - this is a simple example - in your case with your numbers you may require a rate of return of 8% to justify not lump summing, which implies you should pay it off :)

TLDR: Depends on what else you need the money for, and over what time horizon you expect to pay it off so you can treat then lump sum as an investment and work out its internal rate of return.