The phrase "a longstanding alternative" is correct and usable in written English.
It can be used to refer to an option or choice that has been available for a significant period of time.
Example: "The herbal remedy has been a longstanding alternative to conventional medicine for many people seeking natural treatments."
Alternatives: "a long-established option" or "a time-honored alternative".
An expansive exhibition of Polish art has taken over Real Art Ways, a longstanding alternative art space in Hartford founded in 1975.
"I think that Kickstarter or similar programmes of its ilk will form a longstanding alternative to the traditional model of funding coming via large investors or publishers," Neil Barnden, co-founder of Stainless, told the BBC.
A growing number of new snowboards are going "green" this winter, heralding a change in manufacturing practices that has found some brands challenged to adapt, and others gaining belated recognition for their longstanding alternative approach to making boards.
Additionally in the current study, internal medicine and pediatrics had some of the most longstanding Alternative Payment Programs (i.e. established in 2003 2005), which may have lessened the concern of physicians in responding to a survey about billing behaviors making them more likely to respond compared to the other specialties.
speed limit--a longstanding joke!
In January this year the commissioner wrote that he has a "longstanding interest in complementary and alternative medicine and in its relationship to astrology".
"The Dissent Channel is a longstanding official vehicle for State Department employees to convey alternative views and perspectives on policy issues," spokesman Mark Toner said in a statement.
"Not only of architectural interest, the venue has a longstanding historic role as a symbol of tolerance and alternative entertainment".
Adidas is a longstanding partner.
"It's a longstanding belief".
This is, of course, a longstanding position.
