First, if you have 7 years to decide if you want to exercise it, then every stock option has risk-free upside regardless of the strike price. Without the 7-year rule then the upside isn't so clear cut, but that doesn't mean they are near worthless at all.
Second, companies really don't grow that quickly. Over a 1 or 2 year time horizon, even a really successful company will 2x-4x in value (and the common stock might grow even less than this). If the strike price was low on the original grant, the strike price will also probably be pretty low on the refresher grant. Especially at early stages of a company's life when the options are priced at essentially zero, even if you 5 or 10x the value, the strike price will still be very low.
When you have more established companies and higher strikes prices, it is less of an issue because there might be a shorter term path to liquidity which takes away risk of exercising without being able to sell the stock.
That said, your point about having 7 years to decide is entirely fair, and mostly negates that downside.
On the other hand, if it's an amount of options you can afford to exercise (e.g. 1k shares @ $5 = $5k… most people could scrap together the funds for that.), your profit is unlikely to be more that 2-5x, which likely would return $10k, and at the most $25k on your $5k investment. A lot of risk and trouble to go through for very little gain…
That said, with a 7+ year time period to exercise after leaving the company, it's not an issue