If you keep your part of the bargain, the insurer must
keep theirs. As long as you pay your premiums on time
and comply with the terms of the policy, the insurer
cannot cancel the policy or increase the premiums no
matter how many claims are made. Part of your responsibility
is to keep the insurer informed about changes in your
circumstances, such as a new job. They will usually
then have the right to reassess your premium. If you
go from being a telephone operator to a nightclub bouncer,
you are likely to face a steep hike in your premiums,
based on the the obvious increase in risk to your health.
If you become unemployed for any reason not covered
by the policy, you must still inform them. They will
probably be keen to discontinue the policy (at least
until you return to work), as you do not have an income
to protect!