As I see it, when a Bull Trend is going to change, you better be pretty good at sensing it.
Having credit spreads over several months, leaves you wide open to wipe out. The further you go out, the less likely you are to have gained enough to even break even on a credit spread.
Lets assume you have a dozen credit spreads in Bull Put Credit Spreads under a Bull Market. If they are 60 or 90 days out, you are going to get hit when the market indexes takes a drop. Everything goes down, at least 98 % of it. The exceptions are not enough to worry about and would be in individual stocks. I just don´t yet see how closing them before hand, or after the event is going to get you out without big losses. You can make money with credit spreads if you are good enough to anticipate the Bull Market ending and swiveling on a dime. A 5% or 10 % index drop you need to be out of bull PUT credit spreads completely before hand and if you have credit spreads scattered over three months, you just are not going to be able to close them in anticipation of the Bear Market drop, even if it is just a deep correction without losses.
On the other hand, if you are in short term credit spreads, you might be able to close them BEFORE the drop, or have less and less of them. It is easy to make money with credit spreads in a Bear Market drop by just piling on the Bear Call Spreads, by laddering down, on each pull back. But you need same month, or even weeklies to do this.
On the other hand, if you are smart enough to ladder down a Bear Market with Bear Call credit spreads on each pull back, or following a simple 45 degree trend line on a chart, it is a waste of cash money, or margin to be doing credit spreads. You should be just doing straight PUT options. The profit is bigger, supposedly unlimited to the drop, why waste your money on a limited profit spread at 3% or 5% when your straight PUT options will earn you 30% to 50 % for the same moves?
Credit speads in my view are only good in a long slow Bull Trend. They allow you to collect time decay, without losing option value to TIME DECAY. Even then, a monthly would be best. Even so, sharpening your skills at reading the market and playing the short term corrections in a bull trend with straight options, will still return you 30% or so on each short term reaction and back to the trend. In and out in four days instead of months and cycle your money more often.
Credit spreads are supposedly safer trading, lesser profit, in a trend. But fine tuning your chart reading skills will get you more and safer profit in the long run, just making short moves. Heck one trade a month, will do better than playing credit spreads. There is the rub, people cannot learn the patience to only play a sure thing. It´s impatience and greed that wipe you out.