we have 3 large Hornbeem trees in front of out condo. they are 35 to 40 ft high & quite bushy.they are located aprox 50 ft from the building & there are no power or telephone lines near them. we have been told that unless they are pruned regularly their root systems will spread excessively & will eventually pose a threat to the building. is this true? one influential resident seems determined to cut the trees down; citing as reasons that it is too costly to have them pruned often & if they are not pruned their root systems will pose a threat to the building. any opinions?