Yes, I have done several 100 mile trips, but not in Maine. Can't help you with the bug question or specific local logistical issues. The following observations usually apply to most backpack locations.

As a "rule of thumb" estimate your time on the trail as 2 mph PLUS 1 hour for each 1,000 feet of elevation gain. This rate is an average all-day rate that includes a 10 minute break each hour. It is a good rate for a moderately heavy pack (say 35-40 pounds). I would also add 1 hour each day for stream crossings, map reading, etc.

A 10-mile day on the flat would then be: 10 miles x 2 mph + 1 hour contingency = 6 hours.

A 6 mile day with 3,000 feet elevation gain would be: (6 miles x 2 mph) + 3 hours for elevation gain + 1 hour contingency = 7 hours.

Elevation gain is a summation of all the uphill you do -- it is not endpoint minus start. I count the contour lines that the trail crosses and multiply by the contour interval. If you use the TOPO program you can just draw a line of travel and do a profile and this is all done for you!

Good pre-trip planning will save you a lot of grief on the trail. Know where the camp sites are, where you access water and have some options for each day --a few more miles you can add if you are ahead of schedule and a few miles you can shorten the day if you get behind.

The key for me to make my daily mileage, is to get up early and get on the trail by 8:00-9:00 AM. You should be able to get up, cook breakfast, pack up and be on your way in 1.5 hours or less. If you cannot do this now, practice until you can easily do this. It usually takes me one hour from wake up to on the trail. Also be aware of your rest-break time. It is really easy to have the breaks drag into half an hour. The problem with long breaks is that if you cool down too much it is hard to get started again. When I keep a slow but steady pace and break no more than 10 minutes per hour, I always get a "second wind".

For a 10-day trip I usually start with a bit under 40 pounds- about 10 pounds of gear that I carry + 1.5 pounds of food per day. I wear about 3-4 pounds of clothing and shoes and seldom carry my trekking poles on the pack so do not count that weight as "weight on the back". With good planning on the food, you can get about 2,600 calories per day with 1.5 pounds of dry food. I use a butane stove and the largest cannister (about 13 ounces) lasts me for 10 days.

On longer trips, particularly solo, I sometimes loose self-motivation. I like to have a pretty well laid out ittinery, so if I wake up with no motivation, I do not have to think too much - just do the scheduled hike for the day.

A light pack is also the key for your first long trip. If your "big five" are not light, I would consider renting lighter gear if you do not want to buy new gear. Also pare down the list of all those little items that you really do not need. With a lighter pack, I can get by with light hikers or low-cut hiking shoes that are more comfortable. I would rather hike 100 miles in good fitting trail runners than klunky old boots any day. Be sure to break in your shoes before heading out.

In the big picture of long-distance backpacking, 100 miles is not too long - a perfect distance for your first long trip. Good Luck.