The biological definition of the verb “transpire” means to give off water vapour through a pore or stoma. This usage of the word indicates that the mistress’s “willing soul” is seeping through “every pore,” giving her a flushed appearance as her skin is lit with the “instant fires” of her passion. The speaker seems to be saying that while she is still young and in possession of a willing and passionate soul, they should consummate their love.
"Deserts of vast eternity..."See in text(Text of the Poem)
Rather than thinking about an afterlife or framing eternity as something sweet or romantic, the speaker instead conceptualizes it as a desert. He implies that the future does not hold joy or an often imagined blissful paradise; rather, it is instead barren and dry. There is nothing there for his lady and him, so they should instead make the most of their love while they are youthful.
Vegetables grow slowly and take time to develop, much like the how speaker’s love for his lady would if only there were more time available to them. As it is, they do not have the time. So, despite the speaker’s desire to dote upon his mistress for thousands of years, he instead urges haste so that villainous time cannot steal away the love they have in the present.