Been a hairstylist for 28 years.........your hair grow on average 1/2 " a month. If you get highlights, keep in mind that you will start seing some regrowth every month. Depending on how long your hair is, if it's layered (more or less, if you have a style when you have a part and see the scalp, you will noticed the regrowth.
At first, your highlights are going to show a lot more. Because it will be new to you and because hair products usually darkened the highlights (build up), if you use a hairspray, first spray it on a kleenex, if it's light brown then you know that colour will deposit in your highlights (hair is more porous when highlighted).
Keep in mind your hair will lightened up over the summer. Depending on your hairstyle and length, you will need to get them freshnened up between 2 1/2 to 4 months. If you've never had highlights before and afraid of getting it done. Ask your hairstylist to give you highlights that are suttled.
Depending on your haircolour, age and hairstyle and what you want to achieve, there are many options.
Gisele