With any sort of high mileage plan, you WILL lose speed, even IF you do strides.
Why? Because for strides to be at their most effective, they must be done when your legs are relatively fresh.The key for maintaining your speed, is to do strength/speed building exercises at a sufficient level of raw speed. Speed is not about perceived effort, or how it feels. It's literally about how fast your legs are moving, and your body's ability to make adaptations to that speed.
If you're on 100mpw, that means you're running at least 13 miles a day. There is literally no way that your legs are going to be fresh enough for you to be able to muster that "raw speed", and your body is going to be too busy recovering from that 13 mile exertion, to make a 100% proper adapation to your strides/speed. You can probably maintain/limit the loss of your speed to some degree, but it's going to be very hard and an uphill battle.
Think about a weightlifter doing the bench press. He can do a max of 380lbs of 4 reps and 2 sets. He suddenly decides to do 10 sets of 30 reps at 45 pounds everyday to build his endurance. He can try to maintain his strength by throwing in some heavier reps, but he won't come close to doing even a single rep of 380lbs after 10x30 of 45lbs.