I feel you, DH is gone ALOT as well. Right now we are getting ready for him to be gone between 9 months to a year. This is the longest stretch he has ever been gone for and Im dreading it. We have 3 children (4. 2. and 3 months) so things are hectic, now I get to do it solo. Things I usually do when hes gone:
I stay up an hour or so after the girls/baby go to bed. This is ME time. No cleaning, cooking, planning etc I can only do something that recharges me. So I read, sew, knit, do cross stitch, watch a tv show/movie. Sometimes I take a hot bath and eat chocolate ice cream. Yea, super indulgent there but SO worth it if its been a LONG day.
Don't be afraid to ask someone for help. Im horrible at this but even if its just a couple of hours of adult conversation its so worth it. Im blessed we just moved from overseas to Florida to be with DH's family while hes gone. Its going to be nice to have adults to talk to that I can also trust with the children.
Stay active. Join a book club or library time, find a musuem that does a childrens program, volunteer in church etc. DON"T sit around the house. Sitting around makes the time go at a snails pace and it can bring down your mood. Do something to keep yourself and your children happy.
Pick a new skill for you/your children to work on while your husband is away. Ive potty trained two children, learned to knit and learned to decorate cakes while DH has been away. My oldest learned to count, learned her colors, learned the alphabet etc while Daddy was gone. She loves to think of new things to learn while hes gone to "impress" him when he gets back. Her newest goal is to learn to read so she can read him a Christmas story over Skype for Chirstmas.
Have a loose schedule. I find my girls are a lot easier to deal with when we stick to some kind of loose schedule instead of winging it.
This might sound bad but my girls have "chores" to help around the house. They help clean their playroom, they clear their plates off the table, my oldest refills her and her sister's water cups when they need to be, they help when I need to clean.. They LOVE it but I do feel bad somewhat that my girls will run to help people empty their dishwasher It gets things done quicker which means we all have more time to relax.
Quiet time is also something I do to calm everything down. 30 minutes to 1 hour a day where everyone has to be engaged in a quiet activity. The girls like to color and Ill cross stitch, read or lay on the couch with my eyes closed.
Sometimes I find its easier on me if the girls aren't worked up with him being gone. My middle especially is a totally daddy's girls so anything I can do to help them understand how long hes going to be gone for.. Like:
Think of something to mark the passage of time as a celebratory thing if its getting hard. When DH is away for more than a couple of weeks each Wednesday we have a "movie night" where we have a picnic dinner and watch a short movie or part of a movie together. Sometimes if I know exactly when he will be back I separate the movie into parts and tell them that when the movie is all the way over then Daddy is coming home that weekend/whatever day it is hes coming. If the children are having a really hard time with him being gone try count down chains. Since you know how long hes going to be gone just make a reuseable one with 5 chains on it and then take one off for each day during the week. I usually hang one around the ceiling although sometimes it gets really long (Ive had it around the whole front room before). My girls have fun making them. i find the easier it is on them the easier it is on me