Have lasted all this while.
The flowers he "nearly bought" could be refering to the future they almost had together. She may not the refering to the regret she had for the relationship, but rather just a sense of bitterness, of how it could have been.
You did. You’d come along
Unfulfilled promises, this man is capable of saying but not of completing the task.
Who pay no praise or wagesNor heed my craft or art
The reference to "the lovers" here could be a reference to the author, or the character he's representing, himself; that he is writing for people that is similar to him.
twofold silence
If this represents the death of one (or both) lovers, the silence here would not only be in their control. They stay silent because that is the only way to show their love to each other.
Hangs like a blue thread loosened from the sky:So this winged hour is dropt to us from above
This could be the reference to a inevitable, painful moment that is bound to happen, and in this sentence the author uses a very interesting comparison of fate to "a blue thread", bound to be loosened. This could suggest regret, sorrow or even acceptance
n your fragrant bosom dies
Bosom here could be understood as the care, and in this sentence he could be refering to how their relationship is at stake
finger-points look through like rosy blooms
In this sentence, other than the life that her finger give, the author could also be referencing the gentleness of her touch, the colors of the mentioned fingers.
For in your eyes they sit, and there
I think this is a very interesting take on the "sparkle in the eye" of a human being, could be a metaphor for innocence.