Years ago I talked about this issue with a friend who is a botanist and a landscape gardener - his advice was: don't make a science project out of this question. It's quite simple: on poor soil you will need fertilizer at once - on rich soil you will see when you have to fertilize - the performance of your plants will decline, if the nutritients are consumed.
If you grow plants with special needs, you will have to test your soil and to improve it, if it doesn't meet the special needs of your plants.
If you grow perennials for their flowers, choose fertilizers that stimulate flower induction; if you grow perennials for their leaves, choose fertilizers that primarily support growth of foliage.
If you are not satisfied with the results on your daylilies from using compound fertilizer, try rose fertilizer - it improves the performance of any flowering plant. This advice turned out to be right in my garden (situated on gravel ground - the neighbours grow mainly thistles and weeds).