18 months ago I was training for a HM and got really bad shin splints, I got a shoe fit done as I tend to be more of an under pronator and once I had my new trainers which are brooks go-2 s I never had any more issues.
I have been training for my first sprint tri which is this Sunday and can feel my shin splints slowly starting to niggle.
I'm wondering if its my trainers getting worn although they haven't really had excessive use in the past year, or maybe just because I have increased my running pace and volume recently. I've only been running 5k per session though .
I battled shin splints for 3 years. I could only run 3 days a week because my legs hurt so bad. I finally realized I was just running to hard. Always trying to beat my lasts runs time. Took a month off to heal. Started training by HR and slowed down a lot. Run almost every day pain free. I am also faster now too.
I have also had great luck with ART - specifically rolling a tennis ball on the opposite side of the front of my shin that is affected (for me, the shin splints are on the inside of the shin, so I roll the outside of the shin) as well as lots of calf stretches. Here is a great site about self treating with ART that I use for a variety of things (I have no affiliation with them - just really like the site):
Buying a new pair of Shoes would be the first thing I would do if the current ones were more then 4 to 6 months old you say they are about a year I would ditch them for sure. I would also stick to some softer running surfaces for a week or so, trail's Open Fields, baseball diamonds rather then sidewalks or roads.
Even if you are only running 3 mile a week 3X that's about 500 Miles for the year, replace the shoe's