Roughly, how long does eviction fluid last! Thanks

That depends upon how much was used initially, what it was applicated too and was it placed in or out of the weather/ sunlite etc. A well made product should last for weeks if not months based upon the initial information I posted.

Animals have a much greater sense of smell as has been stated here many times then that of us humans.

Therefore residual odor can be there for a long time if placed on an absorbent surface or material and not eaten by mice, chewed by squirrels. Or has been diminished in mass or has significantly evaporated due to heat or UV and dried out in some manner to where there is little to no odor.