Q. Is there a difference (for brocho achrono) between the time of digestion for solids, which is usually 72 minutes, and that of liquids?

A. Shulchan Aruch (O.H. 184: 5) rules that there is no difference between eating solids or liquids and one should recite the Brocho Achrono as long as he is not hungry or thirsty which is usually the for seventy-two minutes
.See question 32 in this forum were we wrote in regards to drinking coffee during Shavuos night. Mishnah Berurah (185 – 17) writes that as long as the individual who has recited a brochoh, has not diverted his attention and keeps his intention on continuing drinking (even if the food or drink has been already digested) he does not have to repeat the brochoh. However the responsa of the Shoel Umeshiv (Tom. 5-23) states that if more than a half an hour passes after finishing each cup he should recite anew (comparable to the four cups of the Seder). Similar is the opinion of Chukei Chaim (s-1), who maintains that after a lapse of two hours he should repeat the brocho, especially if he has to leave his place of learning and prepare a cup in another room.
Horav Shlomo Miller Shlit”a is of the opinion that if one has finished his drink and now engages in learning, it would be considered heseich hadaas (divertion of attention) and a new brocho should be recited when he decides to drink again. As for the brochoh achronoh responsa Minchat Itzchak (5 -102) opines that the time for digestion for liquids is rather short and one should recite that brocho immediately after he finishes drinking.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a