This depends partly on the terms of the insurance and partly on the laws. I work as an actuary and at the moment our company's rules are:

• if the price of the insurance depends on your occupation, you are obliged to report if your occupation has changed and your premiums may be reset to new values (higher or lower)
• if the price depends on whether you smoke, you aren't obliged to report when you start, but we reserve the right to ask you and then you must truthfully answer (and then the premiums may change)
• if the price depends on you weight, only your weight at the insurance start date is important, no need to report later changes (and even if you do - e.g. in case you sign another insurance - your old premiums remain intact)
• if you lie or violate your obligations to report, your benefits may be cut in the ratio of your actually paid premiums and the premiums you would counterfactually pay if you hadn't lied (this is, more or less, specified by the law)

We don't sell any policies which are more expensive for people who are less likely to die (such as pure endowments), but even if we did, I find it hard to imagine that we'd offer lower price for smokers. That would be pretty bad marketing - "insurance company XY motivates their clients to smoke" makes for a pretty diappointing headline. Suing a client for quitting smoking? Unthinkable.

By the way, if I decide to invest in my retirement, I'd want to buy pure annuity without any guarantee or death insurace; I'll need the money if I survive to old age. Unfortunately I don't even know whether such products are ever sold, people clearly prefer to have a guaranteed 10 year annuity or fund transfer to their heirs in case of death or whatever similar, since they are now certain that the insurance company doesn't consume their savings if they die. But it makes the insurance significantly more expensive and most of the advantage the insurance has over bank savings is lost.