Why it's harder with age
Basic LAMal stays guaranteed for life, whatever your age or health: no one can refuse it. Supplementaries (LCA), however, depend on a health questionnaire: with age and possible history, insurers may refuse a new application, set reserves or charge higher premiums. That's why switching supplementaries gets trickier with age.
What remains possible
Keeping your current supplementaries is fine: an in-force contract isn't cancelled for age. On basic insurance you can still optimize: comparing premiums yearly and adjusting the deductible and model remain savings levers at any age. For supplementaries, it's better to keep good cover acquired young than to seek a new one late.
The right reflex: anticipate
The lesson is simple: the supplementaries you'll need later (hospital, care) are ideally subscribed young and healthy, when they're most accessible and cheapest. If you're helping an older relative, focus savings on basic insurance (comparison, deductible, subsidy) and carefully keep the supplementaries already in place.