For 25 years these events have allowed owners to open, test, taste and, if lucky, certify their old bottles of "Bin" wines, the top-of-the-range labels that underpin Penfolds. King of them all is Bin 95, better known as "Grange".

This year more than 2000 people will attend one of the five recorking clinics across the country. They come from all walks of life. A billionaire trucking magnate has dispatched 64 bottles to be assessed, but most will walk in with just a single bottle or two.

"Each and every bottle has a story," says Peter Gago, chief winemaker at Penfolds, and custodian of the legacy of Max Schubert, the man who invented Grange back in 1951. "The majority of people we see bring in one, maybe two bottles. Each is part of their family story. They are wedding gifts, birthday gifts. They have been stored under staircases or in the bottom of laundry cupboards. For a lot of people, they have been in the family for decades."

Penfolds' winemakers will assess more than 10,000 bottles, all of which must be at least 15 years of age to qualify. About three-quarters will be Grange. The lucky ones get to have their bottles topped up, recorked and signed by a winemaker.

One of those making the pilgrimage to the Melbourne clinic is Lesley Crossland, who has stuffed a bottle of Grange in her handbag.

Photo: Mark Hawthorne

Three decades ago she gave that bottle, a 1982 vintage, to her father, Graham Stephens, for Christmas. He cherished it until he passed away. "Dad would bring it out every once in a while, mostly at Christmas, to show us all," she says.  "But he lived in fear mum would use it in the bolognaise sauce."

To save his beloved Grange from a culinary demise, Mr Stephens tied a little gold ribbon around the neck, a warning to Mrs Stephens not to cook with it. Crossland then had to save it from the wake. "I snuck it out of the house when no one was looking," she said.

After three decades, the honour now goes to Gago to untie the ribbon. Should it pass, the bottle could fetch $500 at auction. It it fails, it will be rendered worthless. "Not even good for the pasta sauce," warns Gago.

"Are you sure you want to go ahead?" he asks, one last time. "This is the point of no return."

With Crossland's approval, Gago cuts off the foil and carefully extracts the 34-year-old cork. He pours just 15 millilitres into a tasting glass, and then allows it to breathe. "The colour is good," he says. After a quick sniff and taste, he looks and up and smiles.  "It's excellent," he says. Congratulations."

Crossland is overcome with joy. "I'm telling my daughter, if she wants to drink it with me, then she had better give me a grandchild."

It's a scene played out across the country, but not all are so lucky. Here in Melbourne, about one in five bottles fails to meet the required standard. The failure rate is much higher for the older and rarer wines, and also in warmer climes.

Gago recalls one man who brought a "full set" – one bottle of every single vintage of Grange ever made – to the company's Brisbane clinic a few years back. "One by one, I had to fail every single bottle," says Gago.  Asked what that full set would be worth if it had passed, Gago replies "millions".

Next up is Alan Porter, who has brought along a 1971 Grange, the vintage that was recently crowned the greatest wine made in the 1970s. The bottle was given to him in 2011 by his four children, to celebrate his 40th wedding anniversary.

The level on Alan's wine is low – a bad sign – but he decides to press on. Removing the foil reveals a cork that is starting to leak. Winemaker Kym Schroeter is nervous. A fail will render Alan's wine worthless.

Should it pass, it could fetch $1500 at auction. The damp cork is removed and, again, 15 millimetres is poured. After a short wait, the wine is tested. "It's a pass," says Schroeter. "Congratulations."

A large smile appears on Alan's face. "Now I just have decide when we drink it," he says.