Jim Cramer thinks recent analyst downgrades on stocks with big runs will test investors.

"Right now, until the end of the year, I think we have one of those moments where you will have to work hard to keep your positions on and not to sell simply because of price," the "Mad Money" host said.

In the past, huge rallies have prompted investors to change disciplines midstream. Instead of selling the rips, they let the gains ride because the market blew through so many levels, the new levels would last.

This is a new environment, Cramer said. The days of toxic gridlock in Washington that prompted investors to sell stocks every time an issue arose and then buy them back when it was resolved could end.

That doesn't mean investors shouldn't take profits on less-deserving stocks, or those that have gotten ahead of themselves that are pure commodity plays, he said. It simply means that right now the hardest thing might be to stay the course, rather than ring the register.

Cramer says it is time to talk about the lack of institutional memory on Wall Street.

"There is almost a whole generation of young money managers out there who have only ever experienced central bank intervention as a positive for the stock market. Call them the quantitative easing generation," Cramer said.

These younger professionals believe that when the Federal Reserve keeps interest rates down, it makes certain stocks more attractive than they would be normally. Thus, they think that the Fed raising rates will put a damper on stocks.

Cramer gets that argument. It's easy for him to see how investors would believe that the market could take a hit from higher rates.

What younger professionals don't know is the experience Cramer saw with his own two eyes over the span of 35 years on Wall Street — that the stock market can still make big moves higher, even if the Fed raises rates.

Shares of Thor Industries skyrocketed more than 12 percent on Tuesday, and it looks like young buyers may have had a hand in the success behind the company's monster recent quarter, too.

Thor is the No. 1 maker of recreational vehicles and motor homes with various brands that include Airstream and Jayco. The company delivered a 26-cent earnings beat from a $1.23 basis, and revenues up 65 percent year-over-year, driven in part by the company's recent Jayco acquisition, which increased its market share in motor homes.

Thor's CEO Bob Martin told Cramer on Tuesday that one of the benefits of having younger buyers of recreational vehicles is their ability to use RVs outside of the campground, such as at tailgates or soccer games.

"For us, getting these younger buyers in at an earlier age really helps the cycle to where once they start camping, they typically don't stop. They typically trade into another unit, typically a larger unit, and for us that is just great news for the long-term of the RV industry as a whole," Martin said.

Ever since interest rates began to rise over the summer, Cramer noted that real estate investment trust stocks, or REITs, have been hit hard as investors seek higher yields from bonds.

EPR Properties is a REIT that owns a mix of entertainment, recreation and educated-related properties. At the beginning of the month it reported a strong quarter, and also announced it was investing $700 million to bulk up the recreational side of its portfolio.

While Wall Street had a mixed reaction, some investors worried that its expected sale of $647 million in stock could create an overhang, given that EPR has only $4.5 billion in market cap. Cramer spoke with EPR Properties' CEO Greg Silvers, who said that the transaction will drive growth for the company.

"We structured this very well. We were very disciplined in our approach. And we think this will be a positive both for those shareholders that stay with us and future shareholders," Silvers said.

Believe it or not, some stocks can even stump Cramer. When that happens, he puts it on his list to do more homework, and then follows up with investors to make sure that they receive a reasoned response. Sometimes, the research is surprising.

Cramer first vowed to do more research when an investor on "Mad Money" asked about Tetra Tech.

Tetra Tech provides consulting and engineering services for companies and governments handling complex problems with water, the environment, energy, infrastructure and resource management.

"I think the future is too murky to own Tetra Tech up here, particularly when you consider how much the stock has run. If you own it, I'd say ring the register, at least until it pulls back to lower levels," Cramer said.

Cramer also provided his take on a few caller stocks in the lightning round:

Alliant Energy: "No, let's go with the one that I own for my charitable trust that we follow really closely. Let's go with American Electric Power, AEP. That's what you want."

Insys Therapeutics: "Man, you are so speculative with that. Too speculative for me."