The answer: a long time. One of the oldest Lorain City Directories revealed that Gideon Serbu had been serving soft drinks at that address since at least 1926. The business description had evolved to include 'billiards' by 1933, and was listed as a restaurant by the end of the 1930s.
Although there was no name listed in the directories during that time, references to the business in newspaper articles from that era refer to it as Carpathian Restaurant, still run by Gideon Serbu. (BTW, Mr. Serbu's 1949 obituary noted that he was born in Romania, so it makes sense that his place was named after the Carpathian Mountains, more than half of which lie in Romania).
While the restaurant listings continued into the early 1940s, by 1942 the address was listed as 'vacant.' There was a one-year listing as the Atlas Athletic Association in the 1947 directory.
By the early 1950s, however, the place had sprung back to life as the Flamingo Cafe, run by Henry Ruth. Throughout the 1950s, the directory listing varied, with other names including Flamingo Bar & Grill and just plain Flamingo Bar.
John Hanna entered the picture around 1960, and the restaurant became Hanna's Flamingo Bar. The 1962 remodeling and re-christening as Hanna's Lounge seemed to be an effort to forge a new beginning.
After that, the place would change names and ownership many times: Pete's Bar (late 1960s to mid-1980s); Tony J's Cantina on the Strip and Tony J's (mid-1980s to late 1990s); Zamora's Crossing (late 1990s).
By 2000 it was for sale. It looks like it finished up its useful career as Cantina Sports Bar; finally, a 2013 listing in the Morning Journal of addresses to be demolished included 2100 E. 28th Street – and that apparently was that.
Today the corner of E. 28th and Oakwood, that had seen so much activity over the decades, is an empty lot. But here's a 2013 view, courtesy of Google Maps.
There's plenty of other things on that August 7, 1962 Journal page that are of interest: a photo of young Carol Sandor of Avon Lake, who had just won the "Tell Me Why!" contest connected with that daily Journal feature; and a photo of a race held as part of the annual carnival of St. Vincent de Paul Church on then-Route 254 (which I attended for a while).
And of course the movie listings are always fun, with a great triple feature of house-themed horror movies at Lorain Drive-in: House of Wax (1953), House of Usher (1960) and House on Haunted Hill (1959).