Valuation of debt finance

Hello Sir, in your valuation of debt finance lecture, you mentioned that the reason we care abt the changes in the market value of our bond is because it affects the capital gain or loss we make on it. But why are we concerned abt it when the premium we’ll be getting on the redemption of the bond is already stated to us? Is this cos we might trade it before the redemption date? And if thats the case, we wont be receiving the premium on redemption or our overall yield. So shouldnt the period to the redemption of the yield be a factor when choosing between bonds?