Last week, Iowa’s longtime Republican Sen. Chuck Grassley turned 80 years old. A few days after his birthday, Grassley made the surprising announcement that in 2016 (when he’ll be 83, for those keeping track at home) he will seek re-election.

In a few ways, Grassley’s move is smart. With the retiring Tom Harkin’s Senate seat up for grabs in 2014 and a ramshackle Republican field in place in that race, Grassley’s decision ensures that any prominent Iowa Republicans gunning for a Senate seat won’t have the option of deferring to 2016.

Grassley has also given a party without many up-and-coming stars a little more time to build up its talent pool.

The move will also preserve some of the state’s hard-earned clout in the Senate, as Grassley said himself last week.

“If Iowa had to start over two years from now with two very junior senators, it would hurt Iowans’ opportunities to get anything done in the Senate,” Grassley told reporters after announcing his intention to seek re-election.

Then there’s the fact that if Grassley runs, he’ll probably win.

According to a June Des Moines Register poll, about 60 percent of Iowans approve of the job Grassley has done in the Senate. The experience of winning five-consecutive statewide elections will certainly help, too.

As Todd, the baby-faced Nazi from “Breaking Bad,” might ask, even after 36 years in the Senate, how do you turn your back on more?

But Grassley’s decision, which would likely keep him in Washington until the age of 89, raises that most uncomfortable of questions: How old is too old?

It’s a question we deal with in virtually every election cycle. In 2008, we fretted over John McCain’s age. Today, some folks are worried about Hillary Clinton’s age, and she hasn’t even announced whether she’s running.

Concerns about age are often overblown as they pertain to the physical health of the candidates in question. Grassley, for example, is a pretty fit guy who looks undeniably good for 80. I’d take a fit 80-year-old over a 60-year-old in poor health.

But there is a particularly insidious problem with electing older politicians again and again.

Assuming he wins in 2016 and calls it quits before the 2022 race, Grassley would retire having served 42 years in the Senate. That means that during Grassley’s tenure, two full generations of Iowans will have come and gone without full representation in the Senate.

That’s two generations of unique experiences, perspectives and values that will be more or less skipped over, at least in Iowa’s Senate delegation.

I’m not one to advocate for term limits or mandatory retirement ages — both policies cause more trouble than they’re worth — but I do respect a politician who knows when to hang it up and pass the torch to the next generation. Harkin’s surprise decision to retire in 2014 at the relatively young age of 74 is a good example.

Grassley’s decision to stick around a while longer isn’t all bad — six more years of the senator’s tragically unhip Twitter account is a victory in my book — but every word we get from Grassley comes at the expense of the voice of younger generations.