I think dropping collision also depends on usage:
I have a truck that I use on my farm to haul materals, trash, hay, etc. Since it only gets driven off the farm once per week I dropped collision on it, even though it is still worth $10k (value has actually started climbing the last 2 years). It helps that it stays under a barn so it is protected from hail and tree limbs. In a busy year I only put 5k miles on it.
The family car, however, gets driven a couple days a week and much further distances so I waited until about $3k to cancel it. Just a higher risk due to the higher miles.
Definitely increase deductible to $1k as soon as you have that much in your savings to cover it.