training for the marathon is not like building a pizza where you can just throw on a handful of Jalapenos and turn it into something else. you can't just take published training plans and bolt them together as though they were Lego bricks or something and expect a PB to pop out the end like some magic child's toy.
it doesn't work like that.
training is a long term endeavour. it takes patience, and commitment, and dedication and focus on a goal. you can't just flit from one thing to another like some woman at a department store makeup counter trying out new shades of lipstick.
make a decision.
what is it that you are training for?
then build a program that takes you from where you are to whatever it is you want, and along the way you can run some races at other distances but you have to always bear in mind that they are not the goal.
on the other hand, if you don't want to do that, if you just want to flit through life like some lost butterfly dancing from one flower to another drinking in the nectar where you can find it then there is no problem to solve and your question is irrelevant. just run. do speedwork when you feel like it, run a marathon off 5k training. achieve nothing.