pitkäaikaissä
Pitkäaikaissä is not a standard or widely recognized term in Finnish. In established dictionaries and textual corpora, the form does not appear as a defined concept. When it is encountered, it is most often the result of a typographical error, a mistaken compounding, or a very limited, nonstandard usage. Because of this, there is no agreed-upon definition or scope for pitkäaikaissä in mainstream Finnish.
The phrase appears to be built from the stem pitkäaika-, meaning long-term, and the locative suffix -ssä
Because pitkäaikaissä lacks an established meaning, it is not appropriate to rely on it in formal writing
Pitkäaikaissairaus, pitkäaikaishoito, pitkäaikainen, pitkäaikaisuus.