During the hot summer months it is very important to water your hostas. I have a lot of people ask me why at the end of the season my hostas still look good while their hostas look all ratty and brown. One of the big reasons is that I keep my hostas watered well during the summer. Hostas don't always act that other perennials which will droop and tell you when they want to be watered. However you will see the effects of the dry spell eventually, usually late summer. Hostas alway develop a second flush of leaves in July, so by keeping them watered you will have a much better looking plant.
There are two other reasons why my hostas (not all) don't look all ratty at the end of the year.
1. Slug are attracted to hostas and will eat the leaves. You usually will not see them, because slugs come out at night to do their damage. I lay down slug bait, such as Sluggo, to keep slugs off my hostas.
2. I am also picky about where I buy my hostas from. Don't buy from the big hardware stores! A lot of their hostas have hosta virus X. I have even been to some local garden stores and seen the virus. Last year I even asked for the manager and pointed out the virus to them. I stopped by a week later and the plants were still for sale. Buy from people who have a true passion for hostas and are concerned about the spread of the virus and another hosta enemy, nematodes. Nematodes will cause your hostas to develop wholes and brown streaks in the leaves late in the summer and spread by water.
Here is more information:
Hosta Virus X: http://www.inthecountrygardenandgifts.com/articles/hosta_virus_x.php
Pictures of nematode damage: http://www.hostalibrary.org/diseases/nematodes.html