I have a 50,000 keyword max too. Others have more, some have less. They won't reveal what determines one's limit, however I'd imagine it's either CTR or spending amount. Another Google "secret" for some reason.
I have no trouble managing my account even when working on a relatively low end PC. When I get at around 49,000, I look for what I can clearly live without and then add more campaigns/adgroups/keywords.
I'm curious what you mean by "I'm not sure my ads always show correctly". If you describe in detail, I'll watch for it.
patient2all
I normally run on an 800MZ PC and it's a tad clunky navigating. When I use my other 2.4 PC, it flies (I don't use the 2.4 as much since I haven't had time to install all the software I need on it yet).
I recall one thread where AWA inferred that your ads can be managed better with less keywords rather than more, but I doubt that has any impact on my ads showing. They show when they show, driven by many other factors, of which I doubt the # of keywords is one.
In fact, I've found that the more possibilities I include in an AdGroup, the more profitable it tends to be. When for lack of imagination, I only use say 15 keywords in an Adgroup, it's rarely a big moneymaker.
My best AdGroups have between 150-300 keywords, making sure to include plurals and other likely variants. Keep in mind that broad match is very undependable, especially for smaller niches. With less history, it appears that Google simply isn't sure how to expand on it. I've found that using the articles 'a' and 'the' where appropriate help a lot. 'green widget' as a broad match (or phrase for that matter) often won't match on a search for 'a green widget'. Sometimes though it will.
My oldest campaigns often match too broadly according to my logs. You have to keep adding negative keywords to avoid what you don't want to show for. Especially with adult related campaigns. Computers simply don't understand how sex works ;)
Matching flexibility appears to be based on how many impressions 'green widget' has accumulated and how 'green widget' performs when shown for expanded broad matching possibilities.
I'd like to say myself that I am using very targeted keywords and have a great many distinctive AdGroups and all would profit if I had more flexibility.
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To address your original question, I don't believe that sheer # of keywords has had any impact on how often my ads are showing or at what position, etc. Hardly any of my words go on hold, I usually replace them when I see they aren't getting impressions anyway. Still, it would be handy if I could keep a second account to use as a benchmark to see if a more lean account has any bearing on profitabilty. That would violate TOS though.
patient2all
For example, in one of our long-established accounts that we were adding a significant number of keywords to, we ran into the 50k limit quite quickly, which we were able to have raised to a a 1 million keyword limit because the account "qualified" for this raise.
These limits are really not system limitations (though the account does load more slowly with several hundred thousand terms) because clearly they allow it in established accounts, but rather Google's effort to avoid keyword-spammers or inadvertant abuse by novice users? Any thoughts on this?
Mike