They don't like 'wet feet' and they do like to have humus in the soil. Leaf mould is good. Heads in the sun and cool feet - like Clematis. And they appreciate a topping with an organic mulch. If you plant them in company with shrubs ensure they get reasonable sun during the day. If you got the bulbs locally they probably won't need lifting for winter protection. And they don't like being out of the ground for too long - unless you leave them in a box with potting soil to protect their scales. Even when they lose their stems and leaves, they never get to be as dormant as a daffodil. If the scales develop a deep purple shade the bulbs have probably become too hot and dry. You might only get short stems and no flowers the following year. Leave enough room for daughter bulbs to develop around the original mother plant and form a larger clump. Some of the asiatics develop stem bulbils which drop off and start to sprout on the ground's surface. Some lilies have two sets of roots: basal which are the first ones and are like daffodil roots; then another set which are very close to the surface and come from the stem not the bulb itself. They're feeding roots, which is why mulching and a humus-rich soil is so good for growing good lilies. Expect stems 3' plus. Don't sniff the orientals too closely - they're generous about sharing their pollen, and it can stain.

You mentioned that you all in idaho still get frosts until the first of june. So if the lily bulbs are not yet sprouted I say you could plant them right now and that will allow the bulb to establish a root system. However if it has started to sprout already it increases the risk of frost damage. A late frost can kill the plant, or stunt the flower growth.

They really don't need to be divided as often as you think. The plants themselves will tell you when it's time as they will become very congested and not bloom well. I have left them in place for as long as 5 years before needing to dig and separate and replant. If you do decide to divide this year, wait until the flower stalk has ripened and aged to brown and the foliage is dry, in late summer/early fall. Dig carefully, divide or separate the bulbs and replant right away.

My new favorite is Sunshine Flower Bulbs. Their catalogue is online. Because I ordered so many lily bulbs, they called me and offered to let me buy wholesale, so now I can buy everything they sell wholesale, with free shipping over $150. Everything I bought came up and bloomed beautifully. Last fall I purchased 200 Orienpets and received very large healthy bulbs at a wonderful price. Can't wait to see my lily bed in August! I'm now getting ready to order Asiatics, as they have a good sale going on. On sale are mainly the larger size bulbs, which is a very good bargain. They are new, but I highly recommend the company. I have also ordered from Gordon Wild & Sons; they have bulk pricing and I used them to get acquainted with the types of lilies and to fill up a bare spot. Their bulbs are a little small, though very healthy and a bargain.