As a business owner myself, I understand the requirement to try and rank for as many keywords as possible, as this is one source of commercialisation. However, it is normally unrealistic to assume that you can compete for every keyword that your website is targeting. Especially with the recent Google Penguin updates, Google are making it a lot harder to rank for a large number of keywords. Having said that though, if you carry out exceptional SEO there is no reason why you shouldn’t rank for a large proportion of your targeted keywords.
The optimum strategy for any website it to prioritise their keyword selections based on competitive factors, your current website, conversion rate of those keywords, and the commercialisation applicable to each of those keywords. Once you have achieved your initial set of keywords, it is wise to maintain the ranking positions whilst progressing to targeting additional keywords. As always, SEO is a long-term approach that if carried out properly is the most effective marketing strategy.